Design Life-Cycle

Tracy Manuel

Professor Cogdell

Design 040A

13 March 2014

Hemp: Materials

Hemp has serious potential to make the textile industry more sustainable. It requires little water and no pesticide, suppresses weeds and pathogens, and improves soil structure for other rotational crops. It poses a serious challenge to cotton (which requires a number of fertilizers and pesticides), and synthetic fibers (whose energy-intensive manufacturing processes leak toxic byproducts all along the supply chain). In light of these unpleasant realities, ecologically-sensitive consumers have begun to train their sites on hemp; hoping it will somehow shear away its dreadlocked connotations, unleash its latent potential, and step forward to save the day. However, although hemp is a wonderfully sustainable, low-maintenance crop, our current mechanical infrastructure for converting raw hemp fiber into fabric lags behind that for other natural fibers. In order to make hemp textiles truly sustainable in the long run, the industry must bring hemp processing up-to-speed, source auxiliary inputs (like dyes) responsibly, and properly repurpose “waste” products and scrap fibers.

Hemp is a cellulosic bast fiber harvested from the stalk of the plant. Like flax, hemp is strong and durable even under tension, making it suitable for a variety of both consumer and industrial uses.[1] Hemp thrives in temperate climatic zones between the 25th and 55th parallel.[2] This alone gives it a distinct advantage over cotton, which grows less widely. Hemp grows well across much of Europe and would likely flourish in much of North America, if not for concerns over the plant’s double nature as a popular drug. (Both the US and Canada declared hemp a controlled substance in the late 1930s, though Canada legalized its commercial production in 1998.[3]) In 2004, experts estimated the global yield for hemp at 105,756 hectares, with France and other European countries leading the way.[4] We can assume the yield has grown since then, due to growing interest in “alternative” fibers and the current trendiness of eco-friendly clothing.

Because hemp thrives across such an expansive geographic region, it is difficult to pin down consistent figures for its agricultural inputs. Though hemp is generally classified as a low-impact crop according to Good Agricultural Practice standards[5], the care and treatment it requires varies widely by region and soil quality. In addition, industrial hemp offers a triple bottom line: bast fiber (long stem fibers used for spinning), hurd (short, spongy fibers for bedding and papermaking), and seed oil (a substance prized for its nutritive benefits as well as its industrial applications).[6] Depending on the desired end product, industrial hemp growers may use a variety of techniques. Here, I assume the most basic scenario for growing long-fiber hemp.

Long fiber comes from Cannabis Satvia, a utilitarian form of industrial hemp that grows taller and lankier than its relative varieties cultivated for medicinal or recreational uses. A typical hemp plant must absorb the “big three” organic macronutrients during its lifetime: nitrogen, phosphorus, and potassium (as provided by commercial NPK fertilizers in a variety of forms).[7] However, hemp intended for fiber use requires relatively little fertilizer. Too much nitrogen makes stems harder to process, while phosphorus and potassium often have little effect on improving fiber yield. An average hectare of fiber hemp requires 75 kg ammonium nitrate, (NH4NO3, synthesized), 38 kg triple superphosphate (Ca[H2PO4]2, synthesized), and 113 kg potassium chloride (KCl, occurring naturally in dry, saline areas as the mineral sylvite).[8] When growers tried replacing commercial fertilizers with naturally-sourced pig manure, the pig waste only increased environmental ecotoxicity by contributing to higher eutrophication and acidification of the soil.[9] Hemp growers may also treat the soil with lime (from pulverized limestone) in order to neutralize acidity and provide trace amounts of calcium and magnesium, though this treatment varies by location as well. On average, hemp requires about 83.2 kg lime for an average production scenario that yields 1000 kg dry, green stems.[10]

Hemp does not require herbicides or pesticides. (Cotton, in comparison, may receive up to 20 treatments within a single growing season.[11]) In fact, most commercial herbicides have detrimental effects on hemp. Other alternative methods of pest control such as solarization (where a plastic sheet is spread over the ground for 3-4 weeks) contribute to plastic contamination that inhibits further processing and are generally not used.[12]

Hemp uses both land and water efficiently. 1 kg of dry hemp matter mobilizes about 300-500 liters of water over the course of its growing cycle.[13] Growers typically spread 55 kg of hemp seed over a hectare, though growers for the textile industry favor the fiber content of densely-packed plants and may use up to 80 kg of seed per hectare.[14] In a study determining the impacts of hemp production, researchers found the annual per capita impact of hemp’s modest land use compared to those of crops like wheat and sugar beets.[15]

As with most crops, hemp growing requires a variety of tractors, mowers, ploughs, and cultivators. For each growing cycle, hemp requires 65 kg/ha of diesel and 64.4 kg/ha of agricultural machinery.[16] All told, this means that 1000 kg of dry, green hemp stems only require 309 MJ diesel and a kilogram or two of processing machinery per cycle during the crop production and harvesting phases.[17]

Freshly harvested hemp plants must go through a series of treatments before they are ready for yarn spinning. Many researchers describe the steps between field and wheel as the “bottleneck” in the hemp production cycle. In fact, the fiber processing of hemp at this stage has changed relatively little in the past 50 years.[18] It marks an area for future improvement if hemp is to become economically and environmentally viable on a large scale, especially in high-labor-cost countries in the West. In addition, the textile industry must learn to maximize the full potential of the plant. Industrial hemp plants are 60 - 70% stem. Each stem is 30% fiber, out of which 20% is suitable for use in consumer textiles. So if an average hemp yield is between 7 to 10 metric tons of dry matter, the fiber yield is only 1.5 to 2 tons.[19] Because hemp processing churns out four units of hurd (short fiber from woody stems) per every unit demand of long fiber, hurds command 80% of all time, labor, and energy of processing. This means the success of the hemp industry will hinge on its ability to utilize and profit from hemp hurds alongside long, spinnable, textile fibers.[20]

Separating out the different fiber types from a crop of hemp requires several steps. After the plants reach a certain height, growers cut the stalks and prepare the stems for retting. Retting separates usable bast fibers from the stalk’s woody core by allowing microbes to break down the pectins that bind fibers to the stem. The water retting method requires the stems to be completely submerged in rivers or tanks. Water retting is extremely water-intensive and contributes heavily to pollution. However, Westernized countries with high-labor-cost and stringent environmental regulations tend to opt for dew retting, wherein hemp stems are harvested and left out in the field to rot.[21] Dew retting takes about 10-30 days as naturally occurring fungi and bacteria break down the stems, though these stems must be occasionally turned through mechanical means.[22]

After the fibers are retted, they pass through a series of rollers in a process called breaking, which crushes the woody core into hurds. The scutching process then separates hurds from long fibers by passing them through a series of mechanized revolving drums.[23] Experts estimate that every 1000 kg of dew retted, green scutched long fiber requires an input of 8000 kg dry, green stems and 595 MJ diesel.[24] Then, the newly separated fibers undergo hackling (or combing) to align the fibers into sliver for spinning.[25] A 2000 kg batch of scutched hemp yields 1000 kg usable sliver.[26] The hemp industry should also take care to utilize the short fiber waste produced at this stage, as it accounts for the same amount of mass as the desired sliver.

A variety of commercial infrastructures exist for turning hemp sliver into yarn, as hemp behaves similarly to other cellulosic fibers (especially bast fibers like flax). Hemp yarn production remains the same no matter the harvesting or retting method.[27] But because different desired qualities of yarn require different production scenarios, it was hard to find specific numbers for this part of the production cycle. I assume this is because a spinning technologies are varied, and that hemp may often be blended with other fibers. For the purposes of this paper, I will assume an extremely basic production chain consisting of rove production, bleaching, and spinning for 100% hemp yarn.

The drawing and twisting of sliver into rove (a finer, more aligned version of sliver better suited for spinning) results in a 5% materials loss.[28] Here, 1000 kg hemp rove utilizes 1050 kg sliver. Bleaching hemp brightens its color and allows for easier dyeing. 1000 kg bleached rove requires 1120 kg unbleached rove, 55.6 m3 demineralized water, and 14.9 GJ natural gas[29] (which is mostly methane and found in underground reservoirs). Because of its low lignin content, hemp can be bleached without the use of chlorine,[30] and manufacturers often use a peroxide bleach recipe. Among other non-specified chemicals, NaOH, Na2CO3, Na4O2SiO2, and H2O2 are used, though manufacturers refuse to divulge exact amounts.[31] (The known materials are: sodium hydroxide, a synthesized caustic soda; sodium carbonate or soda ash, mined in the US; silicon dioxide, a mined and processed mineral, and hydrogen peroxide, synthesized.)[32]

After bleaching and drying, the rove is spun into yarn. The spinning of 1000 kg finished yarn requires 1040 kg bleached rove, 53.3 kg mineral oil, and 13.3 m3 demineralized water.[33] Hemp spinning is less efficient than cotton spinning as bast fibers must be spun wet and be dried by a natural gas-powered generator.[34] However, the energy and materials used in this process still depend on the desired quality of the finished yarn (finer yarns take more energy).

As in the spinning step, the creation of finished hemp textiles from yarn could include a wide variety of methods and ancillary inputs. Hemp yarns may be woven or knitted, two distinctly different processes. Knitting machines create textiles directly from raw hemp yarn, but weaving looms require hemp warp yarns to be sized with either native polysaccharides or fully synthetic polymers.[35] The finished fabric must eventually be desized, which usually requires enzymes such as polysaccharide hydrolase. Consumer textiles often involve different “finishes” (such as flame-retardants, insect-repellants, and UV-enhancements) applied in a wide variety of chemical forms as well as in multiple stages of the process. In my research, I never found a predominant production chain for textile hemp, as finishing treatments vary widely by producer and end product. (Not to mention the fact that hemp textiles are rarely created in the countries in which the raw materials are harvested due to western environmental regulations and labor costs.) But again, for the remainder of this paper, I will assume the simplest finishing scenario possible (consisting of a basic dyeing and washing). In addition, I will focus on the use of natural textile chemicals whenever possible. Since hemp remains part of a relatively exclusive niche market of trendy, eco-friendly goods, we can assume that many 100% hemp consumer textiles would be produced as “naturally” as possible in order to maintain their environmental appeal. 

Consumers and manufacturers alike have taken a shine to these natural textile treatments. Some manufactures are currently trying to revive the use plant-based dyes instead of synthetic chemicals. (The land-use impact of a large-scale, natural dye crop revival remains to be seen.) This “return to the earth” philosophy has also sparked recent interest of natural colorants found in food, timber, and agricultural waste, such as mate tea extracts and olive mill wastewater.[36] But no matter their origin, all natural dyes require the use of a mordant as they do not have a natural affinity for hemp’s cellulosic microstructure. Typical natural dye mordants include alum (obtained from chemically treating alunite or natural clays) and potassium bitartrate (cream of tartar, a natural byproduct of winemaking). After dyeing, fabrics are treated with a weak solution of acetic acid and washed with a nonionic detergent.[37] After that, the finished fabric may be sewn in a factory, (though some garments are dyed after construction).

After production has ceased, it’s important to remember the consumer’s role in hemp’s life cycle. Domestic laundering with water and detergent constitutes a large part of a textile’s net material and energy use. A study on cotton found that consumer use through repeated washing constituted 76% of the energy consumption required by an average bath towel, but I found no comparative study on hemp.[38]

Most consumer textiles have relatively short lifespans. Natural fibers like hemp are recyclable, but dyes, treatments, and other blended fibers makes postconsumer recycling difficult. (I assume that hemp, like cotton, is fully biodegradable on its own.[39]) The textile industry does a good job recycling preconsumer waste (such as hurds), with 78% diverted from landfills and funneled into other applications. However, postconsumer waste remains an issue. Only 48% of consumer textiles wind up as secondhand clothing, and many of the textiles donated to nonprofit organizations end up in landfills.[40] Many of the hemp textiles that are recycled are downcycled rather than upcycled. Through the use of a peroxide solution similar to that of the bleaching phase, hemp fibers can be shortened and repurposed for applications like papermaking.

All in all, hemp still holds a lot of promise for the future. It is a hearty, low maintenance crop that improves the productivity of the land. It produces up to four times as much usable fiber per acre as forests.[41] Its strength makes it flexible for use in a wide variety of settings including nonwovens, papers, and geotextiles, not to mention additional uses for its hurds, seeds, and leaves. But using this “wonder crop” efficiently will require a reboot of its production system and a good, hard look at whether or not naturally-sourced dyes and chemicals are as sustainable as they sound. Though hemp is agriculturally primed to be a long-term, sustainable solution, we need to start investing in the improvement of its production chain right now. However, I believe that the changes we need to make reflect deficiencies of the entire textile industry, rather than of hemp alone. Hemp will be an interesting case study for the future – if the textile industry fails to maximize the potential one of the world’s most inherently sustainable crops, then we will have little reason to believe it will ever operate at the level of efficiency our growing population demands.

Bibliography

Bouloc, Pierre, Serge Allegret, and Laurent Arnaud. Hemp: Industrial Production and Uses. Wallingford, Oxfordshire, UK: CABI, 2013. Print.

Brook, George, Kristopher Lijifors, David Brook, and Andy Stewart. National Industrial Hemp Strategy. Rep. no. ARDI III B-27. Ottawa: AGRICOLA GROUP, 2008. Print.

Chen, Hsiou-Lien, and Leslie Davis Burns. "Environmental Analysis of Textile Products." Clothing and Textiles Research Journal 24.3 (2006): 248-61. Sage Journals. Web. 7 Mar. 2014.

Grifoni, Daniele, Laura Bacci, Gaetano Zipoli, Giulia Carreras, Silvia Baronti, and Francesco

Sabatini. "Laboratory and Outdoor Assessment of UV Protection Offered by Flax and Hemp Fabrics Dyed with Natural Dyes." Photochemistry and Photobiology 85.1 (2009): 313-20. Wiley Online Library. Web. 14 Feb. 2014.

"Hemp Weaving - Centuries of Quality Hemp Weaving." Hemp.com. N.p., n.d. Web. 28 Feb. 2014. 

Industrial Hemp in the United States: Status and Market Potential. Rep. Washington, DC: USDA, 2000. Print.

Ossola, Mattia, and Yves M. Galante. "Scouring of Flax Rove With the Aid of

Enzymes." Enzyme and Microbial Technology 34.2 (2004): 177-86.ScienceDirect. Web. 14 Feb. 2014.

Ranalli, Paolo. Advances in Hemp Research. New York: Food Products, 1999. Print.

Shahid-Ul-Islam, Mohammad Shahid, and Faqeer Mohammad. "Perspectives for Natural Product

Based Agents Derived from Industrial Plants in Textile Applications.” Journal of Cleaner Production 57 (2013): 2-18. ScienceDirect. Web. 25 Feb. 2014.

Sharma, H.s.s., L. Whiteside, and K. Kernaghan. "Enzymatic Treatment of Flax Fibre at the

Roving Stage for Production of Wet-spun Yarn." Enzyme and Microbial Technology 37.4 (2005): 386-94. ScienceDirect. Web. 25 Feb. 2014.

Small, E. and D. Marcus. 2002. “Hemp: A New Crop with New Uses for North

America.” p. 284–326. In: J. Janick and A. Whipkey (eds.), Trends in New Crops and New Uses 284-326. ASHS Press, Alexandria, VA.

Summerscales, John, Nilmini P.J. Dissanayake, Amandeep S. Virk, and Wayne Hall. "A Review of Bast Fibers and Their Composites. Part 1 - Fibres as Reinforcements."Composites: Part A (2010): 1329-335. ScienceDirect. Web. 25 Feb. 2013.

Tomaszewska, Maria, and Anna Jarosiewicz. "Use of Polysulfone in Controlled-Release NPK Fertilizer Formulations." Journal of Agricultural and Food Chemistry 50.16 (2002): 4634-639. Print.

Turunen, Lea, and Hayo van der Werf. Life Cycle Analysis of Hemp Textile Yarn. Rep. Rennes Cedex: HEMP-SYS, 2006. Print.

Turunen, Lea, and Hayo M. G. van der Werf. "The Production Chain of Hemp and Flax Textile Yarn and Its Environmental Impacts." Journal of Industrial Hemp 12.2 (2007): 43-66. Taylor & Francis. Web. 14 Feb. 2014.

Van der Werf, Hayo M. G. "Life Cycle Analysis of Field Production of Fibre Hemp, the Effect of Production Practices on Environmental Impacts." Euphytica 140.1-2 (2004): 13-23. Springer Link. Web. 14 Feb. 2014.

Wikipedia, the Free Encyclopedia. Wikimedia Foundation, n.d. Web. 03 Mar. 2014.

{1}

{2}

{3}[1]{4} Brook et al., National Industrial Hemp Strategy, 3.

{5}[2]{6} Bouloc, Allegret, and Arnaud, Hemp: Industrial Production and Uses, 1.

{7}[3]{8} Brook et al., National Industrial Hemp Strategy, 1.

{9}[4]{10} Bouloc, Allegret, and Arnaud, Hemp: Industrial Production and Uses, 1.

{11}[5]{12} Van der Werf, “Life Cycle Analysis of Field Production of Fibre Hemp,” 17.

{13}[6]{14} Brook et al., National Industrial Hemp Strategy, 4.

{15}[7]{16} Bouloc, Allegret, and Arnaud, Hemp: Industrial Production and Uses, 77-78.

{17}[8]{18} Van der Werf, “Life Cycle Analysis of Field Production of Fibre Hemp,” 15.

{19}[9]{20} Ibid., 21.

{21}[10]{22} Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, E-1.

{23}[11]{24}Van der Werf, “Life Cycle Analysis of Field Production of Fibre Hemp,” 14.

{25}[12]{26} Bouloc, Allegret, and Arnaud, Hemp: Industrial Production and Uses, 92.

{27}[13]{28} Ibid., 100.

{29}[14]{30} Ibid., 105.

{31}[15]{32} Van der Werf, “Life Cycle Analysis of Field Production of Fibre Hemp,” 17-18.

{33}[16]{34} Ibid., 15.

{35}[17]{36} Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, E-1.

{37}[18]{38} Ibid., 7.

{39}[19]{40} Ranalli, Advances in Hemp Research, 75.

{41}[20]{42} Bouloc, Allegret, and Arnaud, Hemp: Industrial Production and Uses, 113.

{43}[21]{44} Industrial Hemp in the United States, 5.

{45}[22]{46} Ranalli, Advances in Hemp Research, 75.

{47}[23]{48} Industrial Hemp in the United States, 6.

{49}[24]{50} Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, F-2.

{51}[25]{52} Ranalli, Advances in Hemp Research, 75.

{53}[26]{54} Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, G-1.

{55}[27]{56} Turunen and van der Werf, “The Production Chain of Hemp Textile Yarn,” 2.

{57}[28]{58} Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, 30.

{59}[29]{60} Ibid., G-2.

{61}[30]{62} Brook et al., National Industrial Hemp Strategy, intro.

{63}[31]{64} Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, G-2.

{65}[32]{66} Wikipedia.

{67}[33]{68} Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, G-2.

{69}[34]{70} Ibid., 49, 30.

{71}[35]{72} Ibid., 8.

{73}[36]{74} Shahid-Ul-Islam et al., "Perspectives for Natural Product Based Agents,” 6-7.

[37] Grifoni et al., “Laboratory and Outdoor Assessment of UV Protection,” 314.

[38] Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, 9.

[39] Chen and Burns, “Environmental Analysis of Textile Products,” 253.

[40] Turunen and van der Werf, Life Cycle Analysis of Hemp Textile Yarn, 256, 258.

[41] Brook et al., National Industrial Hemp Strategy, intro.

Crystal Li

Design 40A

Research Project

Hemp-Embodied Energy

The Life Cycle of Hemp

Introduction

Hemp (Cannabis sativa L.) is an annual crop that grows basically all around the world. It is a very common and easy to grow organically without any artificial processes (“Hemp Textiles in Britain”). In the textile industry, hemp is considered as one of the oldest resources of textile fibers which has the history of over 10,000 years (“Hemp History-Global Hemp”). The earliest use of hemp in textile could trace back to ancient China, 4000 BC, when the Chinese used hemp to make clothes, shoes, ropes, and an early form of paper (“Wikipedia”). It is such an environmentally- friendly plant that is known for multi-purpose, especially in the production of high quality textiles. From the perspective of embodied energy, this research project specifically focuses on different forms and the amounts of energy in the life cycle of hemp in the textile industry. As I was researching online about the entire life cycle of textile hemp, I discovered that hemp is the most ideal crop among other common raw materials that are used in textile production because the energy processes taking place are relatively cleaner, more environment-protective and recyclable.

Raw materials acquisition

Just like other plants, the natural growth of hemp takes place under the applications of mostly solar energy, chemical energy, and mechanical energy. Hemp absorbs straight from the sun and water, and then converts the energy to necessary nutrition through the process of photosynthesis. “Hemp is one of the faster growing biomasses known, producing up to 25 tonnes of dry matter per hectare per year... Approximately, one tonne of bast fiber and 2–3 tonnes of core material can be decorticated from 3–4 tonnes of good quality, dry retted straw.” Because the sources of embodied energy are already clean, hemp only needs very little artificial fertilizer even for mass production. “It is very environmental-friendly as it requires few pesticides, when not grown industrially and no herbicides” (“What Is Hemp”). In Europe, the cultivated areas of hemp were used to reach the maximum until World War Two. However, it started to decline because of “high-labor cost, introduction of synthetic fibers, association of the plant with illegal narcotics, and the large scale production of cotton” (Ranalli and Venturi 4). Despite of the fact that cotton is now the most common material in use in the textile industry, hemp is actually a better material to consider. Comparing to cotton, “hemp can produce 250% more fiber than cotton and 600% more fiber than flax using the same amount of land” (Cholia, "The Top 5 Reasons Why We Should Grow Hemp"). What’s more, hemp fabric is stronger, more long-lasting, and more beneficial to the environment because the process of producing hemp fabric has less chemicals involved. In order to produce high quality textile, “fiber extraction has always been the main utilization for hemp. Fibers were used as a basic raw material for the production of rope, canvas and clothing” (Ranalli and Venturi 4).

Manufacturing, progressing and formation

The process of fiber extraction must be taken place under the steps of harvesting and retting. Harvesting requires mostly machine-power and manpower. During the very first process, hemp is harvested depending on whether it is grown for high-quality textile, for seed, or for fiber and seed. When hemp is cultivated for both fiber and seed, seed is harvested “near maturity with combines modified to cut high off the ground, and then the stems are harvested. The fiber from a dual-purpose crop is usually of lower quality and is often used in low-value applications such as pulp and paper.” On the other hand, as for textile applications, “the crop is harvested when the fiber is at the highest quality” (“Industrial Hemp in the United States: Status and Market Potential”). Good-quality sickle-bar mowers and hay swathers will be used to cut hemp for small acreages, and the knife has to be sharp all the time. For larger areas, more sophisticated equipment will be needed (Baxter, "Growing Industrial Hemp in Ontario").

In the process of retting for high-quality applications, “the bast fibers must be separated from the rest of the stalk.” During retting, a chemical process takes place. Retting “breaks the chemical bonds that hold the stem together and allows separation of the bast fibers from the woody core. The two traditional types of retting are field and water retting...[Although] water retting produces more uniform and high-quality fiber, but the process is very labor- and capital-intensive.” Stems are immersed in tanks of clean water and needed to be monitored by farmers frequently. Farmers who are responsible for monitoring must have certain knowledge about fiber quality so they can determine the completion of retting (“Industrial Hemp in the United States: Status and Market Potential” 5). When retting is finished, crop needs to be “dried to halt the retting process before it damages the fiber... The amount of fiber contained within the stem is around 30% of which perhaps 20% is suitable for textiles” (“Hemp Textiles in Britain”). Since only about 20% from the entire crop can be used for textile fiber, tons of stems need to be retted in order to produce more fibers; such process requires a very large amount of water and energy. More importantly, this process of retting is also dependent on skilled labors. With the above reasons, the method of water-retting is abandoned in many European and western countries because the wastewater from water-retting has caused certain environmental issues.    

Lastly, the most important step of producing fiber is fiber separation from stalks. This process is extremely crucial for manpower even though it is partially mechanized. Hemp stalks are brought to a central location for a mechanical process called breaking. “Stalks are passed between fluted rollers to crush and break the woody core into short pieces (called hurds) separating some of it from the bast fiber.” Next, tow (Broken or short fibers) and line fiber (remaining long fiber from the separation of hurds) are extracted for the manual process of “preparing hemp line fiber and tow for twisting into twine or rope or for spinning into yarn” to produce high-quality fiber. Because the traditional hand-method above is not very efficient, new mechanical development such as using flax breaking and tow processing machinery were invented to reduce capital equipment. However, the value of fiber, especially the line fiber for high-quality textiles, loses during the process (“Industrial Hemp in the United States: Status and Market Potential” 5).

Distribution and transportation

Although hemp can be used to make over 50,000 products in so many fields, and flax tow and yarn wastes are byproducts of linen processing and spinning, the use of industrial hemp still remains a very small portion in the U.S. Market because it is associated of the plant with illegal narcotics, marijuana since the 1910s. “In the September of 1937, hemp prohibition began” (Martino, "How Hemp Became Illegal: The Marijuana Link | Collective-Evolution"). Today, only approximately 30 countries permit farmers to grow hemp. China is now the currently biggest producer in the world of hemp. It is also “the largest supplier of hemp fabric to the United States, followed by Hungary, Poland, and Romania.” Unfortunately, I could only find very limited data on the use of hemp fiber, yarn, and fabrics in the textile industry. Because hemp is prohibited and has certain restrictions to grow in the United States, hemp are mostly imported from foreign countries for further manufacturing. According to the data from “Industrial Hemp in the United States”, presented by USDA, imports of raw hemp fiber and yarn had both increased substantially in the 1990s, but the amount of raw hemp fiber is much more greater than yarn. “The switch from yarn to raw fiber...probably [reflected] the development of U.S. spinning capacity.” Even though there was an increase of raw hemp fiber since the 1990s, no data was available on “how much hemp clothing and household furnishings are imported into the United States.” However, the data also suggested that the U.S. exported hemp byproducts overseas. Since there was no direct information on the uses of hemp byproducts, the report assumed that the U.S. exports “hemp raw fiber, tow and yarn waste, and yarn” to other countries for the main purpose of making specialty papers ("Industrial Hemp in the United States: Status and Market Potential” 9).

Use/re-use/maintenance

The use of hemp can be applied to various fields because it is such a green crop that everything in hemp can be utilized. For example, the stalks, seeds, flowers and leaves of hemp can be used to make textiles, specialty papers, seed oil for food, building materials, industrial products and so on. For instance, except for the great production in specialty papers such as currency, filter papers, cigarette papers and tea bags, hemp is also extremely helpful in the agricultural industry. Based on a research about industrial hemp in the United States, hemp provides many opportunities and benefits for “soil improvement by means of crop rotation”, “weed control, disease resistance”, and “pesticide elimination without disadvantages” (Ranalli and Venturi 2). In the consumer textile market, hemp bast fibers are used to make apparels, diapers, fabrics, handbags, denim, jewelry, and footwear. A diagram about the modern uses of hemp is inserted below for more details. In the report, a study also shows other potential uses of hemp bast fibers in automobile manufacture because they are lighter and more recyclable than the current raw material. Above all, even though it takes a certain amount of different forms of energy from cultivating to processing hemp into raw materials for further uses, the received profits and gained benefits of products and byproducts which are made from hemp definitely overweighs.

Recycle

With high biomass production and low inputs, there has been a revived interest in hemp as a sustainable and renewable source. Just like I previously mentioned, the growth of hemp does not need any fertilizer and pesticides because hemp itself has natural pesticides. Not only hemp requires less water and grows more than many other crops we use as raw materials, such as cotton, in the textile industry, but “it [also] enriches and heals the soil it is grown in, cleans the air, and reduces pollution.” One of the biggest advantage of products that are made from hemp is that they are easily recyclable. One of the studies that I found online was the comparison between the recycling process of wood pulp and hemp. According to the study, paper made from wood pulp can only be recycled up to three times and it requires chloride and blench for the whitening process. As we all know, these two chemicals can pollute water gateways seriously. Hemp paper, however, is “clean... [and]recyclable up to 8 times. ” It only needs hydrogen peroxide which is not as toxic as chloride if necessary. After the recycling process, hemp can be safely disposed in the ground because there is not much chemical involved and the waste can also be considered a fertilizer. The same principle can also apply to the recycle of hemp-based plastics. “Like hemp paper, hemp plastics will actually enrich the soil because they are biodegradable and clean” (“Hemp – One of the Most Healthy Recyclable Substances Around”). Considering the above advantages, the paper production from recycling hemp is ideally a new material to replace wood because hemp is more sustainable and reusable. The entire life cycle of hemp from raw material to waste can be utilized completely since it releases almost zero-emission and does nearly no harm to the environment.

Waste management

The use of hemp does not produce any pollution to the environment; however, the process of extracting fibers from hemp does. Coming out a solution of processing the wastewater is doubtlessly the major challenge in waste management because the process of retting takes quite a large amount of water and energy. The report, “Life Cycle Analysis of Hemp Textile Yarn”, indicates that wastewater is a much more important and serious issue than the emission to air because of the huge volume. The wastewater is not renewable because the lack of additional aeration after water-retting. In addition to depleted oxygen of retting liquor resulting in water-retting, a “characteristic, unpleasant” smell arises from the wastewater due to the accumulation of unstable fatty acids and butyric acid. Because the wastewater is “characterized by a high oxygen demand...it should not be released directly into natural water. The retting liquor can either be spread on agricultural land or treated biologically” (Werf and Turunen 24). According to the report, the retting liquor is pumped into a proper wastewater treatment plant for the process of natural biological cleaning. Unfortunately, not all retting workshops use the same wastewater treatment system, there are still many workshops illegally pour the wastewater into rivers and oceans.

Conclusion

The whole life cycle of hemp is completed by applying different forms of energy. Looking into every major stage from raw material acquisition to waste management, hemp is the most suitable crop and resource for textile production because it is sustainable, renewable, and recyclable. In the very first stage of growing, forms of natural energy from the sun and water take place and provide the crop enough nutrition to grow. After harvesting, manpower and machine power become the two major prime movers for the production and uses of hemp. The application of hemp into various products is so broad that it benefits almost all industries. It releases very little emission, expands the lifetime of general raw materials and remains its quality unchanged with recycling up to 8 times. Even after recycling, the disposal can be safely decomposed into the ground because it contains so little chemical. However, the major issue in the production of hemp fibers is the wastewater from the process of water-retting. Fortunately, with the help of modern technology, developments on processing wastewater with less energy and improving the efficiency of producing high-quality fibers have made significantly.

By the end of this quarter, I believe I have reached the purpose of the research project as I completed researching for the life cycle of hemp in textile industry. I learned about every detail of hemp from its history to modern uses, and to further improvement. My point of view was widened as I discovered that the life cycle for even one single small product was so complicated that it had so many steps and different forms of energy involved. Finally, I was amazed to realize that every individual creature on this planet is created by the transformation of embodied energy.

References

• "Hemp Textiles in Britain." Hemp Textiles in Britain. N.p., n.d. Web. 09 Mar. 2014.

<http://www.ukcia.org/industrial/hemptextilesinbritain.php>

• "Hemp History – Global Hemp." Hemp History – Global Hemp. N.p., n.d. Web. 09 Mar. 2014.

<http://www.globalhemp.com/2001/01/hemp-history.html>

• Wikipedia. Wikimedia Foundation, n.d. Web. 09 Mar. 2014.

<http://en.wikipedia.org/wiki/Hemp#United_States>

• "What Is Hemp?" The History of Hemp. N.p., n.d. Web. 12 Mar. 2014. <http://hemphistory.org/what-is-hemp>

• "Industrial Hemp in the United States: Status and Market Potential. (Section-Harvesting, Retting, and Fiber Separation)" Ers.usda,gov. USDA ERS, Agricultural Economic Report No. (AGES-001E) 43 pp, Jan. 2000. Web. 13 Mar. 2014. <http://www.globalhemp.com/wp-content/uploads/2000/01/ages001Ee.pdf>

• Ranalli, Paolo, and Gianpietro Venturi. "Hemp as a Raw Material for Industrial Applications." Springer.com. Kluwer Academic Publishers, 01 Jan. 2004. Web. 12 Mar. 2014.

<http://link.springer.com/article/10.1007%2Fs10681-004-4749-8>

• Cholia, Ami. "The Top 5 Reasons Why We Should Grow Hemp." The Huffington Post. TheHuffingtonPost.com, 06 Aug. 2009. Web. 12 Mar. 2014.

<http://www.huffingtonpost.com/2009/08/06/the-top-5-reasons-why-we_n_253348.html>

• Baxter, W. J. "Growing Industrial Hemp in Ontario." Omafra.gov.on.ca. N.p., Aug. 2000. Web. 12 Mar. 2014

<http://www.omafra.gov.on.ca/english/crops/facts/00-067.htm#harvesting>

• Martino, Joe. "How Hemp Became Illegal: The Marijuana Link | Collective-Evolution."CollectiveEvolution RSS. N.p., 05 Dec. 2012. Web. 12 Mar. 2014.

<http://www.collective-evolution.com/2012/12/05/how-hemp-became-illegal-the-marijuana-link/>

• Van Der Werf, Hayo M. G., and Lea Turunen. "The Environmental Impacts of the

Production of Hemp and Flax Textile Yarn." Industrial Crops and Products 27.1 (2008): 1-10. Science Direct. Industrial Crops and Products. Web. 06 Feb. 2014.

• "Hemp – One of the Most Healthy Recyclable Substances around." Hemphealers Blog. N.p., 27 Apr. 2012. Web. 12 Mar. 2014 <https://hemphealer.wordpress.com/tag/hemp-recycle/>

• "Industrial Hemp: A New Crop with New Uses for North America." Hemp For You RSS. N.p., 04 Oct. 2010. Web. 12 Mar. 2014.

<http://hempforyou.com/>

• "Characteristics of Hemp." O ECOTEXTILES. N.p., 02 June 2010. Web. 12 Mar. 2014.

<http://oecotextiles.wordpress.com/2010/06/02/characteristics-of-hemp/>

Annie Li

March 11th, 2013

Final Research Paper

DES40A – Cogdell

Hemp Textiles – Waste & Emissions

What are you wearing right now? Consider your t-shirt, your socks, and maybe even your underwear. Chances are, something on your body right now is made from or contains cotton. Not many of us are aware of the processes that come before our purchases. Like the saying goes, “Out of sight, out of mind.” Compared to the “fabric of our lives”, hemp clothing requires the lowest amount of input and has the lowest amount of environmental impact. Although often confused with its illegal counterpart, there are many benefits to using industrial hemp fibers as an alternative to cotton.

In the past, hemp fibers were traditionally used for garment production until the 1920’s, when it was eventually replaced by the emergence of cotton in the market.{82}[1]{83} Prior till recently, only a small market of hemp garments existed. Now that environmental friendliness or “being green” is a growing trend, the use of hemp in our everyday products has increased. “The Hemp Industries Association (HIA) estimates that the total U.S. retail value of hemp products in 2012 was nearly $500 million, which includes food and body products, clothing, auto parts, building materials and other products. Of this, HIA reports that the value of hemp-based food, supplements, and body care sales in the United States is about $156 million to $171 million annually. Previous reports about the size of the U.S. market for hemp clothing and textiles are estimated at about $100 million annually.”{84}[2]{85} Besides being environmentally friendly, there are many advantages to hemp clothing. The strong fibers of hemp clothing allow it to withstand harsh conditions.{86}[3]{87} This makes it durable and long-lasting. In addition, the more it is worn and washed, the softer it becomes without suffering fabric degradation. Hemp clothing can also last six times as long as cotton clothing, making it cheaper in the long run. Now how is hemp fabric produced?

Let’s start from the raw materials. The production of raw materials for any textile consumes the most energy out of any other stage in the process. {88}[4]{89} Due to the costs of machinery production, the price of hemp textile production is usually five to ten times higher compared to the production of cotton or other synthetic fibers. Despite price difference, the benefits from growing hemp outweigh the drawbacks by far. Hemp is the number one biomass produced. Because of its ability to grow extremely fast, hemp produces more fiber yield per acre than any other source. One acre of hemp will produce as much fiber as two to three acres of cotton. While cotton takes about two hundred days to grow, hemp can produce ten tons in about ninety to one hundred twenty days.{90}[5]{91} From the moment you plant it and the moment it emerges from the ground, hemp covers the ground quickly and suppresses the majority of weeds - eliminating the need for herbicides. Since pesticides and herbicides account for more than one-half of the energy in farming, this is a plus not only for the environment, but also for the soil. Along with that, only a small amount, if any, of fertilizer is used. Although hemp requires more energy to grow compared to cotton, for every ton of finished textile, the production of cotton uses twice as much land as hemp.{92}[6]{93} When processing is added into the equation, hemp also uses water four times less than cotton does. This is because hemp can be grown easily in most climates with little to no fertilizer.

Although the crop originates from the temperate regions of central Asia, it is now cultivated worldwide. The raw materials for all U.S.-manufactured hemp products are imported because of the controversy associated with industrial hemp and hemp marijuana. Industrial hemp products are completely legal in the United States, but the cultivation is not. Figure 1 shows the primary energy use for the production of non-renewable materials compared to hemp fibers. The production of hemp fibers shows by far the lowest production energy of all the materials. Most hemp fabrics obtain their colors from natural dyeing processes and techniques such as FRD or “Fiber-Reactive Dyeing” in order to reduce dye run-off, which is harmful to the environment.{94}[7]{95}

Figure 2 shows a pie diagram of the energy requirements of different stages in hemp fiber production. It becomes clear that the agricultural inputs of fertilizers and machinery dominate the results by 65 percent.{96}[8]{97}  In order to resolve this, decreasing the use of synthetic fertilizers and replacing them with organic fertilizers along with minimum use of machinery could decrease the energy requirements of this most energy intensive stage of hemp fiber production. 

How much impact on the environment does hemp have? Since hemp is a renewable resource that comes from living plants, it does not contribute to the greenhouse effect. In fact, hemp fiber can have a positive influence on the reduction of greenhouse gases. The plants absorb more carbon dioxide than any other plant. It gets rid of excess carbon dioxide gas as it grows.{98}[9]{99} Hemp also has a deep rooting system which allows crops that are planted afterwards, such as wheat, to grow better. After being harvested, hemp leaves the ground clean, relatively dry, and loosened for some depth. Researchers conducted a study that showed “a ten to twenty percent higher wheat yield after the cultivation of hemp.”{100}[10]{101}

There are usually two methods in which hemp fabric is manufactured – the traditional organic way which relies on mechanical machinery, or the modern way which relies on chemicals for speed and efficiency. The basic steps in the process of creating hemp fabric are the separation of the fibers, spinning and weaving the hemp fibers into yarn, cleaning and softening, and then dyeing and finishing the product. First, the fibers must be separated. In order to soften and separate the fibers, the hemp must be soaked in water – a process called retting.{102}[11]{103} The modern chemical method uses enzymes and chemicals to separate the fibers, which can alter the quality of the resulting yarn because of the use of chemical processes. The traditional organic method usually takes place in a field near a body of water, and can take up to twenty one days to complete. This method is more time consuming and can also pollute the body of water. Although more time consuming, the quality of the fabric produced is higher and more durable. As a solution, researchers are working on developing a process called “green or mechanical retting”, where a machine is used to separate the fibers instead.{104}[12]{105}

The second step in the process is spinning and weaving the hemp fibers into yarn. Once the yarn is complete, it is used to weave or knit the fabric into products. In this process, there is no difference between the traditional methods and the modern methods since the fibers are just being spun. After the spinning process, the fabric has to go through cleaning and softening. The natural strength and durability of hemp also means that it is not as soft. In fact, hemp is known for its stiffness. Thus, the fabric must be cleaned and softened for customer satisfaction. The chemical methods use “heavy caustic sodas and acid rinses to pulp, clean and soften the fiber.”{106}[13]{107} Doing so strips the fiber of its strength and even results in hazardous, environmentally destructive waste. Afterwards, solvents are then use to scour and clean the fabrics. With the organic methods, cleaning agents used to scour and clean the fabric are biodegradable, unlike the use of solvents. ECOLUTION® is a Romanian based, environmentally-friendly manufacturer of hemp products. It has been researching and developing new methods and machinery to produce organic and chemical free hemp fabrics that are “soft to the skin and yet retain the exceptional durability of hemp.”{108}[14]{109}

Lastly, the hemp fabrics are dyed. Environmental laws in the United States, especially California, regulate companies and their methods and dyes for dyeing fabric. Hemp textiles come in many colors, the most natural one being beige – hemp without any added dyes. With chemical methods, chlorine is most commonly used to clean and prepare the garments for dyeing. Synthetic dyes follow suit.  These dyes are produced in a laboratory from other chemicals and may contain heavy metals and elements that are dangerous when released in the environment. In addition, harmful chemicals are sometimes added to the dye bath in order to help the dye molecules bind to the fibers of the fabric. The amount of energy used to operate the dye machine also varies from country to country. The organic method of dyeing does not consist of chemicals. In fact, the fabrics are finished mostly without the use of synthetic chemicals. On rare occasions when chemicals are needed, corporations make sure that the chemicals used meet strict ecological standards. A new technological advancement uses a technique called “air finishing” which blasts strong gusts of compressed air at hemp fabric to soften it in the finishing stage. Hydrogen peroxide is also used to prepare the fabric beforehand for light or bright colored dyes. Natural dyes made from plants, clay, and insects are occasionally used as well. Although they are “natural” because they come from nature, the process of extracting pigments from them are not always less harmful to the environment. As a matter of fact, it may require more energy usage and harmful chemicals than synthesizing them in the lab would use. “Low impact and fiber-reactive dyes are made from natural components that are water soluble with a fixation ratio of at least 70%.”{110}[15]{111}  There are water filtration sites for dye baths to cleanup waste waters used in the dyeing process.  If the dye bath has additives, they must be biodegradable.

In conclusion, industrial hemp production does not result in significant pollution compared to other crops. It has low impact on climate change, eutrophication, and acidification. Although the environmental impact of hemp textile production is less significant than many others, it is still worth considering how they could be reduced further. Next time you walk into a store in hopes to buy new clothing, remember to think about where the product came from and how it was made. Keep in mind that although the organic, environmentally friendly products might be more expensive, the overall quality of the material is higher. The differences between traditional organic methods versus modern chemical methods are vast. By simply choosing to buy organic clothing, you are helping out an industry that promotes sustainability for our environment and our future. You are helping yourself.

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[2]  Johnson, Renée, "Hemp As An Agricultural Commodity," Congressional Research Service (Washington, DC: Library of Congress, July 24, 2013), pp. 5-6.

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[9] Haufe, Juliane, and Michael Carus. "Hemp Fibres for Green Products - An Assessment of Life Cycle Studies on Hemp Fibre Applications." European Industrial Hemp Association 1 (2011): 6. Print.

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