December 20, 2021

The Role of Industrial Hemp in Carbon Farming

The Role of Industrial Hemp in Carbon Farming

Scientific research has established that industrial hemp surpasses any forest or commercial crop in terms of its ability to absorb CO2 per hectare, making it an optimal carbon sink. Furthermore, the CO2 it absorbs is permanently bonded within the fibre, which can be utilised for various purposes such as textiles, paper, and building materials.

BMW in Germany is already utilising industrial hemp to replace plastics in car manufacturing, which is an additional benefit since it is not derived from oil or other sources. Industrial hemp can be replanted continuously, meeting the permanence criteria outlined in the Kyoto Protocol. It's important to note that industrial hemp should not be confused with marijuana. Industrial hemp is the name given to Cannabis Sativa plant with low levels of THC and used for industrial purposes, which is distinguished from psychoactive varieties by its low levels of THC (less than 0.05%). It has been selectively bred to grow longer fibres and denser plantations, resulting in increased biomass.

Hemp has the potential to be cultivated extensively across the world, even on nutrient-depleted soils with minimal water and with little to no need for fertilisers. Unlike many forestry initiatives, hemp can be grown on current agricultural land, and its incorporation into crop rotations can have beneficial impacts on the overall yield of subsequent crops. Thus, hemp aligns with many Government's objectives of boosting employment and bolstering the economic prospects of remote regions.

A very brief history of hemp

Hemp has been utilised for thousands of years, particularly in the production of naval vessel ropes and paper. However, in the 1930s, the emergence of nylon and plastic marked a shift away from natural materials. Concurrently, the recreational use of marijuana increased, leading to the inclusion of hemp in the prohibition of all Cannabis plants. This mindset, influenced by political pressure from the US, became a global phenomenon and resulted in a negative perception of hemp cultivation. Today, governments worldwide have recognised the value of hemp as a crop, particularly its ability to absorb CO2. Hemp is no longer viewed as a threat and has been encouraged as a valuable resource.

The science behind hemp as a carbon sink

A single hectare of industrial hemp has the capacity to absorb 22 tonnes of CO2. With the possibility of growing two crops per year, absorption is doubled. Due to its rapid growth, hemp is one of the most efficient tools for CO2-to-biomass conversion available, surpassing agro-forestry. The amount of carbon absorbed by hemp can be precisely calculated annually by measuring dry weight yield. The total biomass yield and carbon uptake figures derived from the dry weight yield measurements are highly accurate and not available through any other natural carbon absorption process.

Cellulose, Hemicellulose, and Lignin are the primary molecules that make up the fibres of the hemp stem. Cellulose comprises 70% of the stem's dry weight and accounts for 45% of its molecular mass. Hemicellulose, which links cellulose and lignin, constitutes 22% of the stem's dry weight and contains 48% carbon. Lignin, which is located between the cellulose microfibrils and is used as a strengthening material, makes up 6% of the stem's dry weight and has a complex and variable structure.

Therefore, every tonne of harvested stem contains 0.445 tonnes of carbon absorbed from the atmosphere, which represents 44.46% of the stem's dry weight. Converting carbon to CO2 (where 12T of C equals 44T of CO2 according to IPCC), this represents 1.63 tonnes of CO2 absorption per tonne of UK Hemp stem harvested. Based on Hemcore's yield averages (5.5 to 8 T/ha), this represents 8.9 to 13.4 tonnes of CO2 absorption per hectare of UK Hemp Cultivation.

For estimation purposes, the average figure of 10T/ha of CO2 absorption is used, which is considered a reasonably conservative estimate. However, CO2 offsets are based on dry weight yields measured at the weighbridge. The roots and leaf mulch that remain in situ after harvesting represented approximately 20% of the mass of the harvested material in HGS' initial field trials. The resulting carbon content absorbed but remaining in the soil will therefore be approximately 0.084 tonnes per tonne of harvested material (42% w/w). Based on UK statistics, the yield estimates are 0.46 to 0.67 tonnes of carbon per hectare absorbed but left in situ after hemp cultivation (5.5 - 8 T/ha). That represents 1.67 to 2.46 T/ha of CO2 absorbed but left in situ per hectare of UK Hemp Cultivation. After allowing for 16% moisture (atmospheric "dry" weight), the final figures are:

  • CO2 absorbed per tonne of hemp stem: 1.37t
  • CO2 absorbed per hectare (stem) (UK): 7.47 to 11.25t
  • CO2 absorbed per hectare (root and leaf) (UK): 1.40 to 2.06t

Industrial hemp is a self offsetting crop

Defra reports that the total greenhouse gas emissions from UK farming is equivalent to 57 million tonnes of CO2. With 18.5 million hectares of agricultural land use, this results in an average of approximately 3.1 tonnes of CO2 per hectare of total embodied emissions. Due to its low fertiliser usage and lack of pesticides/herbicides, hemp cultivation has significantly lower carbon emissions than the average crop. Additionally, since the matter remaining in the soil after cultivation roughly offsets the cultivation and management emissions, we can assume that hemp cultivation has a relatively small net impact on carbon emissions.

Industrial hemp replaces unsustainable raw materials

Large scale cultivation of hemp can generate vast quantities of products and raw materials that could potentially replace unsustainable oil-based products and materials, particularly in the construction industry. This substitution can help lock in captured CO2 and create secondary benefits for the global environment. Hemp has the potential to replace a significant amount of tree-derived products, reducing the pressure on existing tree populations and maintaining their CO2 uptake.

Compared to other fibre crops, such as cotton, hemp produces much higher quantities of stronger and more versatile fibre, with lower chemical residue and water footprints. While hemp may require extra processing, its recycling potential offsets some of this requirement. Additionally, industrial hemp has a wide range of uses and produces virtually no waste.

While this proposal focuses on carbon capture, it is essential to note that hemp growers have a valuable crop that is in high demand and can generate numerous products.

To conclude, cultivating industrial hemp in the UK and world wide is essential in our efforts to combat pollution, conserve precious water resources, and enhance soil quality. Industrial hemp stands out as a highly effective means of sequestering carbon dioxide and permanently binding it in the materials it is used to create. Accrediting industrial hemp as a carbon credit generator will increase its appeal as a crop.

Furthermore, the hemp fiber is sturdy and has a wide range of uses, including paper, textiles, and biofuels. The seeds are a valuable source of protein for human consumption and animal feed. This will promote an entirely new industry and decrease reliance on imported goods.

Extensive industrial hemp cultivation in Australia will provide a much-needed economic and sustainable boost to remote rural areas and regions grappling with high unemployment and hardship.

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