Crossing the Gap: How Industrial Hemp Can Lead to Greener Engineering
The hemp plant was one of the first crops domesticated by early people. Prized by societies for
centuries, the hemp plant has been used throughout history to supply communities with
necessities such as food, medicine, and clothing. Presently, hemp is valued for qualities such as
its potential for bio-fuel production and the strength and durability of the fibers derived from the
plant. As a result, hemp has been estimated to have tens of thousands of uses in the modern
world including the production of paper, plastics, textiles, and energy. Hemp is one of the most
useful plants on this planet, and has the potential to lead the world into a new industrial age.
Introduction
Modern engineering has created an ongoing tug-of-war between human progress and
environmental conservation. As of now, the Earth as a whole is in a state of turmoil. Forests are
being leveled at a rate of 60,000 square kilometers a year [1], landfills are continuing to grow
and destroy ecosystems, and plumes of greenhouse gasses are damaging the atmosphere and the
environment as a result. The disharmony between engineering and the welfare of the
environment is an issue that needs to be addressed immediately if we are to consider the security
of Earth’s future. What if you were told that both a decrease in engineering’s environmental
impact and an increase in overall efficiency could be accomplished by a single crop?
Hemp has the potential to recreate the world. The usefulness of hemp products as
industrial materials lies mostly in their ability to perform the same desired tasks as other
materials with less undesirable qualities such as excess weight and waste. This ability to
outperform and complement materials like cement, cotton, and plastic in a more efficient and
environmentally friendly manner is what makes hemp a great material for conservationists and
engineers alike. Hemp’s potential to gap the bridge between conservationism and industry
makes it a staple material for a cleaner, more efficient future.
Hemp Materials
The primary historic use of hemp is for making products such as fabric and clothing.
According to the Columbia History of the World, the earliest known example of human textiles is a
portion of hemp fabric from ancient Mesopotamia (now Iran and Iraq) dating back to around 8,000
BC [2]. Since then, hemp has been used in most historic societies, such as ancient China and
medieval Europe. The material used for making hemp fabric is derived from the bark of the stem,
which can be split into many separate layers of fibers for industrial use. These fibers are one of the
most useful parts of the hemp plant, known for their strength and durability in addition to light
weight [3]. Pure hemp fiber is similar in texture to linen and can serve as an insulating material
because of its ability to significantly resist heat flow. Because of its thermal capabilities and highcellulose content, hemp can be used for both structure and insulation, making it possible to build an
entire house primarily out of hemp-based materials [3], for example the Renewable House by the
company Push Design in Ashville, North Carolina [4] (See Figure 1).
The details of the house’s design will be discussed later in this article.
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Figure 1. Renewable House in Ashvylle, NC. http://www.peakdefinition.com/hemphouse- photos-in-usa-today-article/
In addition to the fibrous bark, the hemp plant has seeds that can be processed in order to
extract hemp oil. Hemp oil can be used to accommodate applications including lubrication,
cooking, cleaning, and even nutrition. Oil production from hemp is seen as efficient, especially
because hemp seeds are not the primary goal of crop production and have an average
composition of around 30% oil per seed [5].
Structure and Insulation
Following advancements in structural engineering within the past century, hemp is now
regarded as an increasingly effective material in small building construction. In the Renewable
House created by Push Design, one of the most marketed materials was hempcrete – a mixture of
hemp hurds and fibers, lime, and cement [4]. The typical compressive strength of hempcrete is 1
MPa (one million pascals), which is only around a twentieth of the strength of regular concrete
[6]. Therefore, hempcrete cannot solely account for the structure of a building, and needs to
complement another material that supports the building’s vertical load, such as wood. Despite
these structural disadvantages, the main attractions of hempcrete are its low U-value and high Rvalue, both terms that indicate a material’s thermal capabilities. The U-value of a material
describes the transmission of heat through a material, while the R-value is an indicator of heatflow resistance. Used separately from cement, hemp insulation has an R-value of 3.5 per inch of
thickness and a U-value of .040, both comparable to the values of about 7 inches of glass wool
(fiberglass) [7]. The high-cellulose content and long length of the hemp fibers also provide more
flexibility to the cement, making hempcrete less brittle than regular concrete and removing the
need for extension joints [3]. Using hempcrete also removes the necessity of extra insulation
such as fiberglass, considering that the product doubles up as an insulator in addition to a
structural material.
In addition to providing structure and insulation, hempcrete is also carbon-negative, a term
used to describe materials that provide permanent removal of carbon dioxide from the atmosphere
[6]. Throughout the process of creating hempcrete, carbon dioxide is first converted to biomass from
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the atmosphere during the growth of the plants. After the production of hempcrete, carbon dioxide
from the atmosphere is then absorbed as the lime calcifies, making the wall grow stronger over the
entirety of its life span [6]. The calcification process also extracts excess humidity from the air
surrounding the structure, preventing mold and ensuring clean, dry air. As is common with hemp
products, hempcrete is biodegradable and can be reused for construction or as fertilizer after
demolition [6].
Fiber Composites
In addition to fabric and construction, one of the newest markets for hemp that is
becoming increasingly popular is natural-fiber composites. Hemp composites are an example of
bioplastics, which are forms of plastic produced from renewable biomass sources in order to be
biodegradable. As of the present, there are numerous biomass sources that can be used to
produce bioplastics, such as flax, starch, and vegetable oil. As opposed to other conventional
bioplastics, hemp composites are valued for thermal insulation, stiffness, strength, moisture
absorption, and acoustic insulation [3]. Plastics formed from hemp are cheaper to produce, have
favorable strength-weight ratios, and provide greater recycling capability even within the
manufacturing process. Many large companies have already realized the potential of hemp
composites, including Porsche, BMW, Ford, and other automobile manufacturers [3].
Automotive companies use hemp composites in parts such as interior lining, structural panels,
and insulation. In fact, several international cars that are on the market such as the Canadian
Kestrel are produced primarily out of hemp products (See Figure 2). Commonly produced hemp
bioplastics are made by integrating natural fibers (up to 50% composition) into a matrix of either
polypropelene or polyester, and are biodegradable [3].
Figure 2. Kestrel, a cannabis-composite electric car.
http://green.autoblog.com/2010/09/20/revealed-canadas-cannabis-composite-electriccar-concept-the/
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Biodiesel
In today’s frantic search for alternative fuels, one of the biggest proposed solutions
available is hemp diesel. In Biodiesel Magazine, a Canadian farmer reported that after
producing 20,000 liters of hemp oil, it had “wonderful properties -- better cloud point and
cetane value than biodiesel made from canola or soy oil” [7]. However, the largest obstacle
behind the production of biodiesel is its scarcity around the United States, where production
still remains illegal. For this reason, according to Arthur Hanks, executive director of the
Canadian Hemp Trade Alliance, it is more profitable for farmers in Canada and other
countries to sell the crop into the food market, where seeds sell for around 45 Canadian
cents a pound [7]
Production and Yield
As a genus, the Cannabis plant has over 400 sub-species and can be found on every continent on
Earth except for Antarctica [3]. Hemp grows very rapidly, producing on average around 25 tons
of dry biomass per hectare per year [8]. Out of a grown amount of biomass, bast (inner bark)
fibers can account for up to around 30% of the total mass, the rest being core material such as
seeds and inner stems. Hemp is also self-compatible, and can be grown in the same plot of land
for several years in a row [8]. During the cultivation of the plant, the soil it is grown in becomes
increasingly healthy due to the fast growth and long roots of the plant. The fast growth prevents
and suppresses weed growth, and the long root system loosens the soil, promoting fertility. The
production of industrial hemp is practiced among many countries in Europe and Asia, with China
as the leading producer at two million acres per year [8].
Obstacles in the United States
Despite the numerous benefits of industrial hemp to both the environment and
engineering, to this day cultivation of hemp faces heavy challenges in the United States. In the
past, hemp was significantly integrated into the economy of the United States, and was used in
both World War II and the Civil War for supplies such as uniforms, canvas, and rope [9]. The
US government even went to the extent to produce a short film in 1942 titled Hemp for Victory,
encouraging farmers to grow hemp to help the war effort [2]. In 1956, after studies revealed
definite psychoactive properties of cannabis, the Narcotics Control Act was passed, making
possession and cultivation of cannabis punishable by a mandatory sentence along with fines [9].
Afterwards, the DEA (Drug Enforcement Administration) was created in 1973, maintaining the
federal illegality of cannabis cultivation without a permit [9]. Contrary to popular belief, hemp
is a cousin plant of marijuana, and has no medicinal purpose due to insignificant amounts of
cannabinoids.
Since the illegalization of cannabis production in the United States, numerous
attempts were made by individual states to uplift the illegalization for economic purposes. After
multiple measures on ballots to allow hemp in states like California, production was finally
legalized in 2013 in Colorado and Washington [9]. Despite recent progress, hemp remains illegal
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on a federal level in the United States, making hemp products and research economically
unpractical because of import costs. However, the recent legalizations of cannabis plants points
to an eventual lift of the ban, once again allowing one of nature’s most useful products to be
integrated into our engineering practices. With widespread production of industrial hemp, the
world can secure the future of the planet and progress into a new age of green engineering.
References
[1] Associated Press. (2012, November). Amazon Deforestation Hits Record Low. The
Guardian. [Online]. Available: http://www.guardian.co.uk/environment/2012/nov/28/amazondeforestation-record-low
[2] The People's History, The Thistle, vol. 13, no. 2, September 1, 2000.
[3] Skaidra Smith-Heisters, Illegally Green: Environmental Costs of Hemp Prohibition, 1 ed. ,
Los Angeles, CA: Reason Foundation, March 2008.
[4] K. Wynn. (2010, August). Hemp House Takes Green Design To A New Level. Huffington
Post. [Online]. Available: http://www.huffingtonpost.com/2010/08/30/hemp-house-takesgreen-de_n_695827.html
[5] J.C. Callaway. (2004). Hempseed as a nutritional resource: an overview. Euphytica. 140:6572
[6] D. Flahiff, " Hemcrete: Carbon Negative Hemp Walls," inhabitat, El Segundo, CA: Internet
Brands Inc, August 24, 2009,
[7] H. Jessen. (2007, January). Hemp Biodiesel: When the Smoke Cleared. Biodiesel Magazine.
[Online]. Available: http://www.biodieselmagazine.com/articles/1434/hemp-biodiesel-whenthe- smoke-clears/
[8] P.C. Struik. (2000, March). Agronomy of Fibre Hemp in Europe. Industrial Crops and
Products. 11(2). [Online]. Available:
http://www.sciencedirect.com/science/article/pii/S0926669099000485
[9] (2010, April). Marijuana Timeline. Frontline. [Online]. Available:
http://www.pbs.org/wgbh/pages/frontline/shows/dope/etc/cron.html
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