A Life Cycle Analysis of Hempcrete

Chanel Moon

Cogdell

6 June 2024

Hempcrete Life Cycle Analysis - Raw Materials

As we fall deeper into the climate change crisis, we may start to wonder how we can change the way we currently go about our days to make life more sustainable. This can range anywhere from how we gather resources, to what clothes we purchase, to how we construct buildings, such as our homes. With overpopulation being a contributing factor to climate change, construction is necessary to maintain housing and overall city planning. As we continue to grow population-wise, we continue to grow as well to meet our need for sustainability and eco-friendly resources. In recent years, a material called hempcrete has become more used and researched. Hempcrete is a bio-composite building block, meaning it is made up of a matrix. In this case, the matrix is made up of a woody core, which is hemp plants, and a binder, which in this case is lime. Due to hempcrete’s raw materials, the properties it holds, and its overall life cycle, hempcrete proves to be an innovative development in sustainable building. 

As a basic requirement for being a sustainable material as well as eco-friendly, the material must have qualities that minimize harm to our environment as well as continue to be reused, recycled, and avoid large amounts of waste, which hempcrete’s raw materials put it at a pretty good start. Hempcrete is composed of hemp, a lime-based binder, and water. The beginning of creating hempcrete starts with the hemp plant. The hemp plant has a quality in which it sequesters or captures carbon dioxide, making it a carbon-negative material. For this quality alone, hemp is pretty sustainable with containing carbon dioxide amounts.  The hemp seeds are planted and grown within 4 months. The fully grown hemp is then harvested and processed into hemp hurds. This process begins by taking the harvested hemp stalks and removing the interior stem of the hemp plant. Following this, any fiber surrounding the stem is removed and the stem is then cut into 6-22 mm pieces, creating the final hemp hurds. Once the hemp has been processed into hemp hurds, the hemp hurds are ready to be combined with water, and then a lime-based binder. The lime-based binder is usually made up of powdered limestone and water. To acquire lime, limestone must first be mined, which is usually retrieved from quarries or mines. When the limestone is collected, it is taken to a site where the limestone can then be crushed into smaller pieces. After this process, the limestone is heated by kilns to cook, or calcine it and make it into lime. This process of collecting the lime to make hempcrete does produce plenty of embodied energy within hempcrete.  When the lime is calcined, it can then be crushed further in order to create the powdered limestone that is commonly used in hempcrete. When the binder has been created, the lime-based binder, hemp hurds, and water can be combined. When being combined, the hemp hurds and water must be mixed before the lime is added in. This is because the properties of the hemp and the lime would cause a reaction called bonded cellulose insulation to one another too quickly before the hempcrete mixture is correctly combined. The reaction-bonded cellulose insulation is what allows for hemp hurds, lime, and water to become hempcrete with some time. When the mixture has reached the desired consistency, the hempcrete can be molded and set to dry for six to eight weeks before being ready for use and distribution. At this point in manufacturing, the hempcrete blocks are ready to be sold, shipped off, or used!

Hempcrete’s raw materials before even being mixed together already make it a pretty sustainable material, so is there more to it? When the hemp, lime, and water combination is all dry, the hempcrete has completed and has a rough exterior that of stone. The hempcrete is rich in cellulose, which allows for the hempcrete to retain carbon. The lime-based binder allows hempcrete to be antifungal, antimicrobial, as well as fire-resistant. When the hempcrete is dried, the lime hardens the material, making it as fire-resistant as most rocks. Hempcrete also has excellent thermal properties, especially if used as insulation, due to the fact it has thermal mass. The thermal mass of hempcrete allows for temperature changes to be less drastic, such as the interior of a house heating up quickly when it is hot outside. If the inside of your home gets hot and humid, hempcrete solves the problem of humidity due to the fact it is highly porous. This allows for the hempcrete to simply retain the moisture and prevent any condensation or damp environments in your home, avoiding any potential for mold growth since it passively releases vapor. With all of these benefits of hempcrete, why is it not growing as quickly as it should be then?

Some drawbacks come along with hempcrete as a building material. An overall lack of knowledge of hempcrete also contributes to being a downside of hempcrete. Due to its slowly gaining relevancy, hempcrete is not a very well-adverse topic in comparison to other building materials such as concrete or aluminum. Hempcrete can be made in a variety of different ways, with different uses, molded differently, mixed in different ways, the list goes on. Alongside this, hempcrete requires more time and has a different technique when it comes to placing hempcrete blocks, making this a skill that would have to be taught and improved upon before implementation. The overall structure of hempcrete is a whole new thing to learn and adapt to. For example, even though this disadvantage was previously mentioned as an advantage, hempcrete being highly porous can also be a disadvantage depending on what structure is being built. Since it retains moisture very easily, the seal between the hempcrete and the lime-based binder can begin to loosen the structure of the hempcrete if in direct water for long periods of time, such as standing water or a source of liquid that may be a constant flow. Alongside this, hempcrete also cannot withstand large amounts of pressure, such as the pressure of a roof. For this reason, as well as the beneficial thermal properties hempcrete contains, hempcrete is often used to create walls and insulation. This gives hempcrete specific conditions in which it can be used to the best of its ability, which is still good progress in the right direction!

It is known that the hemp is planted and harvested before being shaved down to hemp hurds and the limestone is transported from the quarry to a site where the limestone is then smashed. After this, the lime is shipped off to the same site as the hemp hurds. When both the hemp hurds and the lime are at the same designated site, the hemp hurds, lime-based binder, and water are all combined, molded into the desired shape, and set out to dry. Due to the qualities of hemp, lime, and water, once the hempcrete is completely dry, the hempcrete is a lightweight and low to medium-density block of its raw materials. As mentioned at the beginning, hemp has a quality in which it does an excellent job of sequestering carbon dioxide, making hempcrete a carbon-negative material on its own. Due to the fact that hempcrete is a carbon-negative material on its own, hempcrete is a low-density material, and the overall lightweight quality of hempcrete, makes the overall energy put into the transport of hempcrete much more sustainable than more commonly used building materials such as concrete or aluminum.  It can sequester about 19 pounds of CO2 per cubic foot or over 100 kilograms of CO2 per square meter. Hempcrete by itself already captures more CO2 than it takes to create it. Due to hempcrete’s newer relevance, hempcrete has not been researched fully in terms of transportation and emissions from transporting it. However, we do know that the transportation of concrete is about 9.5 kilograms per tonne of production output, which is known to be a much heavier and denser material. Just based on hempcrete’s sequestering ability, it already outweighs the overall global impact it could have on CO2 production and helping to decrease it as much as possible.

Hempcrete is used as a building material and usually has the same shape as bricks. Hempcrete can be used for roofing, walls, insulation, and slabs, with walls being the most common. These blocks are low maintenance and can be used for an estimated 300-500 years with proper maintenance when needed. Since hempcrete is a newer building material, there is a lack of understanding of hempcrete's full potential lifespan. A part that goes into this is hempcrete’s ability in which is retain water and as a result, it may begin to degrade and lose its overall structure if left in constant wet environments, such as constant standing water. This would create a new thing to remember to check on and maintain if ever in any wet conditions, especially with any exposed hempcrete, but would still be considered a low-maintenance building material. 

Due to the overall nature of hempcrete, the recycling options are quite minimal.  Regardless of this, how it can be recycled are extremely beneficial in the long run. One way in which hempcrete can be reused is as a building material once again. This may be building a different structure or home. If not used for building purposes and left abandoned or broken down into smaller pieces, hempcrete is bio-degradable and does not leave any harmful chemicals behind. This allows for hempcrete to be used as a mulch or compost. 

Other building materials such as concrete, cement, aluminum, and steel, are all materials we may associate the most with construction. When thinking sustainably, both the concrete and cement industries hurt our environment due to the fact they are one of the main producers of carbon dioxide, about 0.9 pounds of CO2 for every pound of cement, which is almost a perfect 1:1 ratio, alongside being 8% of carbon emissions for the entire world. However, both of these materials do well in terms of keeping their overall integrity as well as their structure for a long period. Another material, aluminum can be recycled and reused, however, it leaves behind a huge carbon footprint in order to manufacture for distribution. Steel is also highly recyclable and can be reused for different purposes. However, it stays around for only about 50 years and is another energy-intensive material to manufacture. There is a pattern among these materials and their flaws which are major in contributing to the climate crisis, which hempcrete can help fix. In comparison to these developments, hempcrete is arguably a much more sustainable and innovative building resource. Although hempcrete is not able to take the place of cement or concrete due to its less dense nature, it can still be a step in the right direction with having a sustainable construction system.

Hempcrete’s raw materials along with its overall lifecycle prove it to be a sustainable development in building resources. Hempcrete can be around for hundreds of years, providing great thermal insulation, and helping decrease overall carbon levels. Hempcrete’s natural composition allows it to be a valuable resource in construction’s potential to work towards bigger climate action in the quickly approaching future.

Bibliography

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Hanna Dewey

Professor Cogdell

Energy, Materials, & Design Over Time

05 June 2024

The Embodied Energy of Hempcrete’s Life Cycle

As it stands today, concrete is the most popular building material in the world. While this material has been greatly useful for constructing most of the infrastructure that we see today, it has immense negative consequences on the environment. Cement contributes to eight percent of the total emissions produced globally each year (Skinner and Lalit). Reports of rising global temperatures and projected climate change call for degrowth and reduced development, yet simultaneously current demands for housing and infrastructure call for a necessary boom in construction. The juxtaposition of these two global needs have subsequently influenced an effort towards designing sustainable alternatives to cement that can concurrently reduce the environmental impact of construction while meeting developmental demands. Hempcrete is the most notable outcome of this effort. By examining hempcrete’s lifecycle from raw materials to end of life disposal, this essay will analyze the intricacies of the embodied energy that comprises hempcrete while simultaneously comparing hempcrete to traditional concrete and therefore providing insight into the environmental benefits of hempcrete. 

Hempcrete is a biocomposite composed of a mixture of hemp, hydrated lime, and water that can be used as a natural alternative for construction. Hempcrete is the most practical sustainable alternative to cement due to its relatively low embodied energy and similar strength and durability to cement. Embodied energy is defined as the total energy that is consumed to produce a product (U.S. Environmental Protection Agency). In this case, the factors that comprise the embodied energy of hempcrete include raw material acquisition, manufacturing/processing, transportation/distribution, use/maintenance, and recycling/disposal. Embodied energy is often described using energy units such as kilowatt hours and megajoules. It is important to note that a kilowatt hour should not be confused with a kilowatt because they measure two different things. According to Direct Energy CA, the main difference between the two is that “a kilowatt is a measure of power and a kilowatt-hour is a measure of energy; power is the rate at which something uses energy, and energy is the capacity to do work” (Direct Energy CA). Similarly, megajoules are also a measure of energy. One megajoule is equal to one million joules. For context, one joule is equal to “the energy used to accelerate a body with a mass of one kilogram using one newton of force over a distance of one meter”(Dictionary.com). The context of these terms will allow a better understanding of the embodied energy that accumulates throughout hempcrete’s life cycle. 

The first step in the life cycle of hempcrete is the acquisition of raw materials which includes hydrated lime, hemp, and water. These ingredients all require some form of processing and transportation, which means they all contain embodied energy. The raw material with the lowest embodied energy is water. Because water can be filtered and treated a multitude of ways and can be sourced almost anywhere, it is extremely difficult to calculate the exact embodied energy. Additionally, not a single hempcrete producer states where or how they get their water. However, a simplified study conducted by Paula Melton at Building Green states that it takes about 1.1kWh (kilowatt hours) of electricity to treat and transport one hundred gallons of tap water on average (Melton). The primary energy sources used to treat water are mostly coal and oil which is turned into fossil fuels that power the treatment plants and transportation systems. While this figure could vary significantly based on the traveling distances and sanitation practices of the water, this figure is a fair estimate of the average embodied energy of water. These variations also affect the embodied energy of hemp and hydrated lime.

Hydrated lime is a processed inorganic material that is produced from quicklime and water. This ingredient alone makes up most of the embodied energy of hempcrete due to the energy intensive process of mining, heating, and transporting. According to a report by the Environmental Protection Agency, the total embodied energy of hydrated lime is approximately 815kWh per one ton (Research Triangle Institute). The first step of making hydrated lime is mining limestone from quarries, which requires large fossil fuel powered vehicles and machines that are often highly fuel inefficient. Once the limestone is acquired through mining, the material is put into large hauling vehicles that transport the stone to large kilns that heat the limestone to 1000 degrees celsius (1,830 °F) (Mellor). This is the ideal temperature needed to turn calcium carbonate (limestone) into calcium oxide (quicklime) which is the precursor to hydrated lime (Mellor). This heating process uses approximately 3.75 megajoules of energy per every one ton of quicklime that is produced (ChemEurope). From here, hydrated lime is made by chemically combining the quicklime with water. Hydrated lime requires a mixture of 72-74 percent quicklime and 23-24 percent water (National Lime Association). In order to accurately calculate the embodied energy of hydrated lime, the embodied energy of water (1.1kWh/ 100 gallons) must also be considered. 

The final and most crucial raw material, hemp, has a low embodied energy. According to an energy analysis done by researchers at Science Direct, less than one megajoule of electricity is used for every one kilogram of hemp shives produced (Florentin et al.). The production of hemp consists of farming the hemp plants until they are fully grown. The shives of the hemp, which are the wooden core of hemp plants, are often a waste product of medical and recreational marijuana hemp production (Yuen). The strength of hempcrete is attributed with these shives. The embodied energy of farming hemp consists of the farming equipment and machines that are used to maintain the hemp fields as well as cultivate it. These machines are majoritively powered by fossil fuels, which is a secondary energy source of the primary energy source coal. 

Once all of these raw materials have been acquired, the next step in the life cycle of hempcrete is manufacturing and formulation. This aspect of the life cycle is exceptionally energy efficient since it can be done with little to no heavy machinery and does not require many steps. The production of hempcrete is simply made by combining the lime, hemp, and water together. This can be done on a small scale, like a bucket, which only requires the energy of a human, or it can be done on a large scale, which requires commercial mixers like those used for concrete. If the mixing process is done by hand, the embodied energy of manufacturing hempcrete is zero megajoules per ton, but if heavy machinery is used, the embodied energy of hempcrete production can be high. Unfortunately there is no data or evidence about how much energy is required to mix one ton of hempcrete, however data regarding the energy usage of mixing concrete is a practical comparison since the processes are similar. On average a typical cement mixing truck uses about 4-4.5 gallons of gas per hour of operation (Peiris). To put this into perspective, a single gallon of gas has an embodied energy of 35.24 kWh (U.S. Energy Information Administration). So, for every hour that concrete is being mixed, an embodied energy of 140.96 kWh is acquired. While this is useful, it is not entirely accurate to what the embodied energy of commercially mixing hempcrete would be since hempcrete is much lighter than concrete which would mean it would require much less energy to mix. However, given that information on this emerging technology is limited, this estimate is insightful. 

The next step in the life cycle of hempcrete is transportation and distribution. The embodied energy of this aspect of the life cycle can vary deeply depending on the proximity of the hemp production to the site of use. If hempcrete is going to be poured into a site directly then the hempcrete is mixed on site which means transportation distances are zero. However, if the hempcrete is made into blocks then these can be made anywhere and also be shipped anywhere. Nonetheless, hempcrete is most likely to be mixed on site due to the advantage of pouring wet hempcrete. One key advantage of hempcrete is that it is much lighter than concrete, almost 8 times lighter (World Bio Market Insights). This means that the energy required to transport hemp is vastly less than the energy required to transport concrete. This aspect of hempcrete’s life cycle is a significant reason why hempcrete is a more sustainable building material. However, the use portion of hempcrete’s life cycle reaps the largest environmental benefit. 

 The use and maintenance phase of hempcrete’s life cycle is arguably the most important environmental benefit regarding hempcrete’s embodied energy. The use of hempcrete can actually sequester carbon dioxide from the atmosphere. While does not directly reduce the embodied energy of the other aspects of its life cycle, it does directly combat the effects of its embodied energy which is arguably equally as important. According to the U.s Department of Energy, the most practical use of an analysis of embodied energy is it's tie to emissions (U.S. Department of Energy). This is because energy production causes large quantities of emissions which directly contribute to environmental degradation. For every cubed meter of hempcrete produced, there is potential to sequester over 100 kilograms of carbon dioxide from the environment (Wang). Furthermore, there is not sufficient embodied energy associated with the use of hempcrete because once it is installed, it does not require maintenance because it is fireproof, mold resistant, and pest resistant. However in the event that the hempcrete does need repaired due to structural damage, it is commonly replaced and discarded instead. 

The disposal process of hempcrete is also sustainable and requires little energy to do. Because hempcrete is made from entirely natural materials, it is easily compostable. The methods of composting hempcrete include crushing the hempcrete and adding it to a compost pile with other organic material. This process requires no fossil fuels or electricity and can instead be done by human power. The composting can even be done on site of where the hempcrete was previously used and be later used as soil on the property. This method of upcycling the hempcrete also produces no waste that must be disposed since it can all be reused as soil. However, it is important to note that in order for hempcrete to be composted properly, it requires appropriate action by the user. Because there is no policy or rules implemented to ensure that hempcrete is composted properly, there is no definitive way of knowing how it is disposed of. 

In conclusion, hempcrete is vastly more sustainable than concrete and acquires much less embodied energy throughout its life cycle. Even though it was sadly difficult to find data regarding hempcrtee’s embodied energy, the data that was available still clearly shows the vast reductions associated with hempcrete rather than concrete. These reduced environmental impacts are associated with hempcrete’s relatively simple production practices, low traveling distances, zero energy usage, and composting abilities. While the environmental benefits associated with hempcrete are great, there is still much more that can be done to even further lower its embodied energy and environmental impact. The largest improvement would be transitioning machinery and vehicles used during hempcrete’s life cycle from fossil fuel powered to clean energy powered as well as increasing the efficiency of such energy producers. Similarly, the kilns that are used to process the limestone which are the largest contributors to hempcrete’s embodied energy can be powered by clean energy or geothermal energy rather than coal and fossil fuels. Nonetheless, even without these improvements, it is clear that the embodied energy of hempcrete is much lower than concrete and yet hempcrete produces the same desired outcome. Consequently, this analysis along with many other academic research findings show that there is a necessary demand for switching to more environmentally conscious building practices, like hempcrete, in order to meet the demands of global development while still reducing environmental impacts and combating climate change. In all, the embodied energy of hempcrete is relatively low and it will likely only continue to lower as this emerging technology is built upon and production is made more efficient. 

Bibliography

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5. Mellor, Joseph William. Modern Inorganic Chemistry - Scholar’s Choice Edition. Longmans, 2015.

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10. Skinner, Ben, and Radhika Lalit. “Concrete: 8% of Global Emissions and Rising. Which Innovations Can Achieve Net Zero by 2050?” Energy Post, 24 Jan. 2023, energypost.eu/concrete-8-of-global-emissions-and-rising-which-innovations-can-achieve-net-zero-by-2050/#:~:text=While%20essential%20to%20building%20the.

11. U.S. Department of Energy. Estimating Raw Materials Embodied Energy and Emissions. 2020, www.energy.gov/sites/default/files/2023-01/2022-12-14%20-%20Raw%20Materials%20PDF%20%281%29.pdf.

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14. Wang, Lucy. “Carbon-Negative Construction.” Anthropocene Magazine, 23 Jan. 2022, www.anthropocenemagazine.org/2022/01/carbon-negative-construction/#:~:text=Hemp.

15. World Bio Market Insights. “Why the Construction Industry Needs Hemp and Fungi.” World Bio Market Insights, 6 Apr. 2022, worldbiomarketinsights.com/why-the-construction-industry-needs-hemp-and-fungi/.

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Emma Saffel

DES 40A

6/4/2024

Professor Cogdell

Life Cycle Analysis of Hempcrete: Waste and Emissions

Many people don't usually attribute emissions and global warming to infrastructure directly, instead maybe transportation, factory farming, or more obviously the direct burn of fossil fuels. However, the built environment plays a surprisingly impactful role in global emissions, most notably through the production, use, and waste of concrete and cement as building materials. In order to alleviate this disparity, a substitute known as hempcrete, a composite made of mainly hemp shiv, has been developed and has begun to make strides for the future of construction. This paper will emphasize that hempcrete generates significantly less construction waste, byproducts, and emissions compared to traditional concrete. By examining each of its life cycle phases, it will demonstrate how hempcrete's lower carbon footprint, minimal solid waste, and potential for biodegradability contribute to its sustainability, promoting its use in future construction practice and discussing its potential to improve even further.

One of the most environmentally problematic stages of concrete as a viable building material moving forward is its production as it releases huge amounts of CO2 and many other pollutants ((Florentin, Y, et al.). In comparison, the production of hempcrete involves significantly fewer emissions, waste, and overall pollution. The primary raw materials that go into hempcrete production are hemp shiv, the woody core of a hemp plant, and lime, a powdery substance made through the calcination of limestone that is used as a binding agent. The cultivation of hemp actually warrants negative emissions overall through photosynthesis, emphasizing the sustainable nature of the product (Arrigoni, Alessandro, et al.). However, the potential use of fertilizers and pesticides during hemp cultivation risks added greenhouse gas emissions through the release of ground-level ozone and the leaching of nitrogen, causing algal blooms downstream (Heimsoth, Josie). Luckily, hemp as an industrialized crop yields much less waste in byproducts, while necessitating overall much less water and fertilizer than most other industrialized crops (Yano, Hiroyuki, and Wei Fu). Additionally, hemp fiber, seeds, and the derivation of cannabidiol oil (CBD) are today's most common uses for industrialized hemp (Yano, Hiroyuki, and Wei Fu), making hempcrete's use of hemp shiv, as a byproduct of existing processes, even more sustainable. Concise and accurate statements about the labor conditions and transportation of this raw material alone are scarce at this time due to the very recent federal legalization of the hemp industry in 2018. However, the industry has gained significant traction since then and hemp can be grown in a variety of climates, so transportation is likely comparable to that of any other common crop. 

Lime production, on the other hand, is a much less "green" part of hempcrete's production. Lime begins as limestone, which is a common sedimentary rock that is then extracted mainly through strip-mining (Laveglia, Agustin, et al). On the global environmental scale, the use of heavy machinery in this process releases many emissions, and on the local environmental scale, this work is a respiratory health hazard due to the dust output, and also worsens biodiversity and contaminates and disrupts groundwater supplies, then causing the potential for sinkholes (Yulex). The limestone is then processed, releasing CO2 through almost every step of the way, and lastly calcinated to create lime. After calcination, the lime is chemically hydrated to become the hydraulic binder, which is another carbon-intensive process, although less so than the step of calcination. Processing limestone throughout these stages does pose variable health risks as getting the powdered product in your eyes, skin, and lungs is very irritable and even toxic (Laveglia, Agustin, et al). However, with proper equipment, these risks can be entirely avoided.

Comparatively, hempcrete uses less lime than regular concrete and overall releases much less emissions and waste than concrete in the production stage, as well as through its initial implementation onsite. The acquisition of raw materials lime and hemp shiv have notable alternate effects on the environment that cannot be directly offset. Still, in terms of sole emissions, hempcrete production is actually carbon-negative overall. Throughout the paper, I will be referring to hempcrete in its form as a "mix", rather than the additionally processed and manufactured block. However, it can be noted that the pressing and drying of the blocks "proved to be negligible compared to the overall impact of the wall" (Arrigoni, Alessandro, et al.) and similar to emissions put out in construction by mixing, spraying, and drying the hempcrete during application. The application of hempcrete using these techniques does not present any issues for labor workers in terms of health risks through airborne wastes if handled appropriately, as do many other aspects of the construction process (Yadav, Madhura, and Ayushi Saini).

During its use phase, hempcrete continues to exhibit environmental benefits with minimal negative effects, contributing to reduced emissions and improved indoor air quality. Considering the distribution and transportation of hempcrete before it reaches direct use from consumers, the transportation of finished products does contribute to emissions. However, the overall impact is lower compared to the transportation of traditional building materials due to the lighter weight of hempcrete (Essaghouri, Laila, et al.). Another way hempcrete is able to reduce potential emissions in its life cycle is indirectly through its efficiency in insulation. Often used as an infill for walls, buildings insulated with hempcrete have lower energy requirements for heating and cooling due to the material's excellent thermal insulation properties (Muhit, Imrose B, et al.). This way less energy is used to heat and cool and the reduction in energy use can be up to 45% as recorded by Muhit, Imrose B, et al., translating to an indirect reduction in emissions. Another interesting insulation effect minimizing an often overlooked form of pollution is its ability to absorb noise relative to other materials (Florentin, Y., et al. ). Of course, if used sparingly, this doesn't have much impact on the broad environment past added comfort for those in shared housing, but it does serve as an added benefit to hempcrete in this facet. Hempcrete is non-toxic and does not release any airborne pollutants in the use stage, this also means it does not need to be coated, which spares any additional potential emissions and toxins released (Arrigoni, Alessandro, et al).  

Lastly, an outcome of the lime binder in hempcrete is its carbonation in the use stage of the life cycle. Carbonation happens when the hempcrete begins to cure, and the processed lime (calcium hydroxide) in the mix reacts with carbon dioxide in the atmosphere to form calcium carbonate. Hempcrete's open, porous structure facilitates this ongoing carbonation process, allowing CO2 to penetrate and react with the lime binder more effectively, sequestering more CO2 from the air over time (Di Capua, Salvatore Emanuele, et al.). This process does occur in regular concrete, but at a much smaller scale due to density and reducing net emissions by much less due to the initial CO2 output of production (Arehart, Jay H., et al.). Additionally, it should be noted that the "maximal quantity of carbon dioxide that can be re-absorbed is equal to the quantity released during the calcination" (Pretot, Sylvie, et al.). So carbonation can be seen as an offset to the production of lime within the overall hempcrete production, not as a negative emission, which is often misrepresented in informal reports about the benefits of hempcrete.

             Hempcrete's lifespan and end-of-life are yet to be universally studied and understood, as it remains a new technology with recent implementations. However, even in the past decade, more about this material has been uncovered signifying even greater understanding in the near future. A source from 2014 talking specifically about the use of hempcrete in France admits that although "it's recycling seems possible…[it is] yet to be developed" (Pretot, Sylvie, et al.), more recent sources have been published that discuss optimistic and innovative outlooks for how hempcrete can be reused and recycled. What we know more clearly now is that hempcrete is biodegradable, and breaks down readily through microbial action, leaving behind nutrient-rich compost suitable for various applications (Muhit, Imrose B, et al). Additionally, it does not leach any toxic chemicals, compared to regular concrete or cement. If efficiently biodegraded at end-of-life, this would minimize landfill impact and environmental disruption through the emissions that would be released if put in a landfill without enough oxygen or otherwise incinerated. Some issues that remain around this is if there are sufficient systems in place for hempcrete to actually be bio-degraded after use, rather than sent to a landfill alongside other construction waste materials. Other ideas for repurposing at end-of-life or even with any excess mix from construction discuss repurposing the material as mulch or utilizing it in waste-to-energy incineration to generate electricity, although this requires clean combustion technologies to avoid air pollution and greenhouse gas emissions (Yadav, Madhura, and Ayushi Saini)​​. For a new and promising technology like hempcrete that has the ability to be biodegradable and sequester CO2 throughout its entire use and end-of-life, the most stress needs to be placed on the importance of creating and maintaining accessible systems for end-of-life treatment and making sure consumers understand how to access these systems. While researching this part of the life cycle, finding fact-based and explanatory information about end-of-life that went beyond simply saying "it can be recycled" was very difficult. Therefore, despite being a relatively new technology, the end-of-life prospects for hempcrete show significant potential through effective waste management and recycling strategies, and the importance of responsible consumption.

Comparing hempcrete to traditional concrete, it becomes evident that the most significant emission and pollutant-releasing aspect is the production of the hydraulic lime binder used in hempcrete. Lime production involves substantial CO2 emissions and environmental pollution due to the mining process, followed by the many steps to process the raw material into hydraulic lime binder. Despite this, hempcrete still offers a more sustainable alternative due to its lower overall emissions and the ability to sequester carbon over its lifecycle. Future innovations, such as the development of magnesium-based binders, present a promising advancement. Magnesium binders have been shown to increase the strength of hempcrete and offer higher compatibility with organic fillers, thus enhancing the material's performance while potentially reducing its environmental impact​​. Magnesium-based binders, such as magnesium oxychloride and magnesium phosphate cement, exhibit excellent mechanical properties and could further lower the carbon footprint of hempcrete production​​ while improving structural integrity (Barbhuiya, Salim, and Bibhuti Bhusan Das).

In conclusion, despite the emissions associated with lime production, hempcrete's overall lifecycle results in a net negative carbon footprint, making concrete and cement incomparable in terms of sustainability. This is due to its carbon sequestration capabilities during the hemp growth phase and the ongoing carbonation process of the lime binder during the material's use phase. Additionally, hempcrete's biodegradability and potential for recycling or repurposing at the end of its life cycle contribute further to its environmental draws. As research and development continue to optimize alternative binders and construction techniques, hempcrete stands out as a sustainable and eco-friendly building material, poised to play a crucial role in reducing the environmental impact of the construction industry. Future innovations and consumer responsibility in its waste management, potentially further enforced by government policies, hold the potential to enhance these benefits even further, making hempcrete not just a viable alternative, but a superior choice for sustainable construction practices. All in all, hempcrete exemplifies how modern materials can evolve to meet both ecological and structural demands, leading the way toward a greener and more resilient built environment.

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