Mariola Kopcinski Ph.D., Global Agrochemical Business Manager at Ingevity Corporation
Agriculture production depends on the availability of several natural resources including soil, water, climate conditions and a variety of biological processes. At the same time, agriculture has a major impact on the global carbon cycle and is a major contributing factor to climate change. There is growing consensus on the need for climate-smart agriculture, driven by international awareness of the sector’s negative ecological footprint. There is also more recognition that conventional forms of agricultural production are often unsustainable and deplete or ″mine″ the natural resources.
Agriculture is the world’s leading source of methane and nitrous oxide emissions, a substantial source of carbon emissions, and the principal driver behind deforestation worldwide. Some 24% of global greenhouse gas (GHGs) emissions are attributable to agriculture, forestry land use, and crop and livestock production for food, fiber and fuel1. While agriculture emits a large volume of GHGs, its biomass and especially its soils also sequester carbon out of the atmosphere. This role as a carbon sink and as a carbon store can be strategically optimized through proven farming techniques including the use of crop protection and nutrition products, which support plant growth and reduce GHGs emissions. Biodegradable and biobased ingredients, like Ingevity’ kraft lignosulfonates, can provide additional benefits for carbon sequestration, as is described below.
Types of soil carbon
Soils contain three significant carbon pools: labile, less labile (recalcitrant) and inert fractions. The labile soil carbon pool consists mainly of soil organisms, polysaccharides, celluloses, and hemi-celluloses with a half-life in soils varying from weeks to months. The recalcitrant pool consists of lignins, lipid polymers, suberins, resins, fats, and waxes with half-life varying from years to decades, and inert carbon pools are deep layers of carbon which if not disturbed retain carbon for thousands of years2.
Carbon sequestration in agriculture
Carbon sequestration in the agriculture sector refers to the ability of agriculture lands and forests to remove carbon dioxide from the atmosphere. Carbon dioxide is absorbed by trees, plants and crops through photosynthesis and stored as carbon in biomass in tree trunks, branches, foliage, roots and soils. Forests and stable grasslands are referred to as carbon sinks because they can store large amounts of carbon in their vegetation and root systems for long periods of time. The oceans, soils and forests are the largest carbon sinks on the planet.
The ability of agricultural lands to store or sequester carbon depends on climate, soil type, type of crop or vegetation cover and management practices. The amount of carbon stored in soil organic matter is influenced by the addition of carbon from dead plant material and carbon losses from respiration, the decomposition process and both natural and human disturbance of the soil. By employing farming practices that encourage carbon sequestration, farmers may be able to slow or even reverse the loss of carbon from their fields.
Role of lignin in carbon sequestration
Lignins are present in all vascular plants and constitute the second most abundant organic polymer on earth, after cellulose (Figure 1). Once plants decay, lignins present in them move to the soil and through organic processes change into the humus, which impacts fertility and water retention. More fertile soil retains more carbon. Since only a few microorganisms (i.e., white rot fungi and a few bacterial species) can completely degrade and fully break down plant lignin, the decomposition process can take many years. As result, lignins are considered carbon sinks if left undisturbed in the soil, especially in the form of humus. Consequently, lignins directly and indirectly influence soil microbial community structure, which in turn controls soil quality through the provision of several key ecosystem services: 1) reducing the emissions of GHGs from the soil, 2) retaining soluble nutrients, 3) promoting soil aggregate formation and stabilization, which reduces soil erosion, and 4) bioremediation and detoxification of natural and man-made organic pollutants3,4.
Figure 1. Typical tree composition
Kraft Lignosulfonates – Polyfon® H – Life Cycle Analysis
To better understand the impact of lignosulfonates, dispersants produced from kraft lignins, Ingevity commissioned a life cycle analysis (LCA) study of its Polyfon® H product by Environmental Resources Management (ERM), a consulting firm based in London, U.K.
The substitute dispersant used for comparison in the LCA was a naphthalene sulfonate formaldehyde condensate, commonly used fossil fuel-based dispersant, and the cradle-to-gate carbon footprint was analyzed. The base case study is a cradle-to-gate assessment that accounts for fossil carbon emissions only. In this conservative base case, Ingevity’s Polyfon H showed a carbon footprint of 1.46 MT CO2e per MT of product. This is based on the energy use, materials, packaging, and wastes associated with the Polyfon H manufacturing process, without considering any potential carbon benefits from the bio-based feedstock. The primary raw material for Polyfon H is black liquor, a waste generated from the pulp and paper industry which carries no carbon burden.
The biogenic carbon contained in Polyfon H would be considered net-zero if it is oxidized and released to the atmosphere as CO2 at end of life, because it was originally drawn from the atmosphere during tree growth. The amount of biogenic carbon is estimated to be 0.60 MT as carbon, which corresponds to 2.2 MT of CO2 .
Because the lignin in Polyfon H breaks down very slowly in the soil, much of the biogenic carbon is expected to remain sequestered in the soil for at least 100 years – the standard impact horizon for carbon footprint studies. Considering the credit of -2.2 MT CO2e resulting from the long-term storage of Polyfon H carbon in the soil, the estimated product footprint becomes negative: -0.74 MT CO2e, if the carbon content remains in the soil for more than 100 years (Figure 2). This result reflects the combination of biogenic carbon in Polyfon H and the fossil carbon associated with materials and energy required to manufacture the product. Assuming at least two-thirds of the biogenic carbon remains stored in the soil for longer than 100 years, Polyfon H will have a negative carbon footprint, i.e., a net global warming benefit5.
This means that Polyfon H, which contains 100% biogenic carbon, completely offsets the volume of GHGs released during manufacturing and generates a carbon footprint 122% lower than the fossil carbon-based substitute dispersant.
Figure 2. Estimated End-of-Life Benefits: Polyfon vs. Substitute (ERM studies)
Carbon sequestration farming initiatives
The United Nations Framework Convention on Climate Change, the Kyoto Protocol, and the Paris Agreement are the significant steps taken by countries around the world to fight climate change. Under the Paris Agreement, a culmination of decades of international efforts, nearly 200 countries have endorsed the global goal of limiting the rise in average temperatures to 2.0 degrees Celsius above preindustrial levels, and ideally 1.5 degrees.
Following the Paris Agreement, more and more companies have pledged to help stop climate change by reducing their own GHGs emissions. In less than a year, the number of companies with net-zero pledges doubled from 500 in 2019 to more than 1,000 in 2020.
However, many businesses are unable to entirely eliminate their emissions, or even lessen them as quickly as they might like. The challenge is especially tough for organizations that aim to achieve net-zero emissions, removing as much GHGs from the air as they put into it. This is where agricultural carbon offsets come into play. Carbon emitters can offset their unavoidable emissions through the purchase of carbon credits awarded by companies and initiatives, many with agribusiness partners or connections, that are committed to removing or reducing GHGs from the atmosphere. This includes U.S. companies carbon credit programs like those offered by Indigo Ag, Bayer, Ciba, and Cargill, and the Solothurn and Ebenrain projects in Switzerland, Kaindorf Certificates in Austria, and CarboCert in Germany. These programs encourage foresters, ranchers, and farmers to increase the storage of carbon from the air into the soil through improved forest, grassland, and cropland practices, which could increase annual carbon storage in the soil by up to 21% of annual U.S. GHGs emissions6. And, with the EU’s European Green Deal in place, which set an ambitious objective of climate neutrality by 2050, initiatives like these are likely to continue to grow in numbers and in scope7.
By simply focusing on better agricultural management practices, farmers can not only reduce GHGs emissions, but they can gain carbon credits while increasing soil fertility and performance. Ingevity’s lignin-based dispersants can further support those practices by reducing the carbon footprint of agricultural formulations and supporting soil carbon sequestration – all of which should be part of regular agricultural soil management.
1. Global Greenhouse Gas Emissions Data | US EPA
2. Scoping Paper: Soil Organic Carbon Sequestration Potential for Agriculture in NSW K Y Chan, A Cowie, G Kelly, Bhupinderpal Singh, P Slavich
3. Lignin controls on soil ecosystem services: implications for biotechnological advances in biofuel crops, S.Gul, S. Yanni, J. Whalen, In book: Lignin: Structural analysis, applications in biomaterials and ecological significance (pp.375-416), Published 2014, Publisher: Biochemistry research Trends Nova Science Publishers
4. Carbon Sequestration in Agricultural Soils, The World Bank Report, number 67395-GLB, May 2012
5. ERM. Carbon Footprint for Ingevity of Polyfon® H and its Substitute. 03.2022
6. The "Carbon Credit Market, By Sector, and by Region - Size, Share, Outlook, and Opportunity Analysis, 2020 - 2027" DUBLIN, Aug. 3, 2021 /PRNewswire/
7. Operationalising an EU carbon farming initiative - Executive summary, European Commissions, January 2021
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