“Reducing the carbon footprint…” You’ve heard people say this before, especially big corporations with marketing stake in the statement. But what does it mean? And what does it mean for us?
When people talk about saving the environment, this movement is a direct response to the warming of Earth’s climate. Global warming is a real threat to our farmers, our wildlife, and the world as a whole. The gas responsible for most of global warming is carbon dioxide, or CO2. Most of the CO2 released into the atmosphere comes from the combustion of fossil fuels for cars, factories, and electricity. Nitrous oxide is another toxic gas that is hurting our environment. Most nitrous oxide comes from fertilizers, industrial purposes, and the loss of our rainforests that would otherwise be storing CO2. While nitrous oxide is 300 times more harmful than carbon dioxide, no gas adds more warmth to the atmosphere than carbon dioxide.
The Hemp Solution
When the topic of conversation moves to global warming, the conversation usually turns a little bleak. But there’s new hope: hemp. Alright, maybe it’s not new. Researchers claim that hemp was the first domesticated crop, back in 12,000 B.C. – and yet, it’s new again. With the signing of the 2018 Farm Bill, hemp is now legal again in the US, opening the door for innovation and environmentally-friendly alternatives.
Hemp begins sequestering carbon the moment it is seeded; conservatively, hemp cultivation yields a sequestration ratio of about 1.5 units of sequestration per unit produced. In Layman’s terms, one ton of harvested hemp fiber should sequester 1.62 tons of CO2.
Hemp can also sequester carbon back into the soil through a process called, biosequestration. In this process, hemp captures carbon emissions from the atmosphere. When the crop is harvested, the hemp can be slow-smoldered, not burned, to create biochar. This charcoal-esque product can then be mixed with other nutrients and returned into the soil. According to a paper provided by Holon Ecosystem Consultants, hemp might give as much as 13 tons of charcoal per hectare annually, which would triple the output of Salix (a popular biomass crop) plantations.
Building and Construction
The first hemp application that usually comes to mind is in building and construction. According to the United Nations Environment Programme, the building sector contributes up to 30% of global annual greenhouse gas emissions and uses up to 40% of all energy. In recent years, Europe has been leading the way back into energy-efficient, hemp-based buildings, with Canada and the US following suit. The most popular in this recent surge: hempcrete. Hempcrete is a fiber-reinforced material made from a combination of hemp hurd, lime, and water. This combination creates a bio-composite material that is lighter and more flexible than concrete while keeping the structural strength and thermal properties ideal for use in non-load bearing construction projects and insulation. But what about its carbon footprint? A life cycle analysis on a 120 square foot
Hempcrete wall would find an emission of 3880 pounds of CO2, but this would not include the materials’ potential carbon sequestration. As we previously mentioned, one ton of hemp fiber should sequester 1.62 tons of CO2 over the growing process, but hemp doesn’t stop sequestering there. Over time, materials in hempcrete undergo calcination, absorbing more CO2. Calcination is the process where materials heat up, below its boiling point, to drive off volatile matter or to effect changes. During this process, and under the same circumstances previously mentioned, the 120 square foot hempcrete wall should sequester 2400 pounds of CO2, leaving only 1480 pounds of CO2 created by the process. Those 1480 pounds are easily offset by the carbon sequestered in hemp production, leaving the entire project carbon negative.
Natural materials are used in hundreds of composite applications. One of the most popular composite applications is thermoplastics. These are a type of plastic made from polymer resins, like polyethylene, polypropylene, polystyrene, polycarbonate, and acrylic. These resins and natural materials can create anything from surfboards to eyeglass lenses. With this much potential, imagine the good that could be done by replacing a little plastic with natural fibers. A study in 2003 by the University of Toronto found that we could save 50 000 MJ, or 3 tons of CO2, per ton of thermoplastic by replacing 30% glass fiber reinforcement with 65% hemp fiber. We can also address the carbon storage capabilities in these natural fiber composites. The same writers of the University of Toronto’s study estimated a carbon storage potential of 715 pounds per metric ton of hemp-based polypropylene composite. This means that the carbon is not sent back into the atmosphere but trapped in the material for years and years.