Agriculture, land use and negative emissions

(Note: this is an chapter from my 2021 book, ‘Planet Zero Carbon - A Policy Playbook for the Energy Transition’. The main themes represented here continue in more detail in my forthcoming book; 'Your Guide to the Energy Transition’.)

While agriculture may be regarded by some as being the less exciting and dynamic aspect of the global drive to reduce emissions and try to bring some balance back to the Earth’s climate; in reality it is agriculture alone that has the most chance of providing the carbon-sequestering potential that will eventually be needed in the long term.

Today, agriculture is in the throes of a what is really a complete overhaul; the flaws in business-as-usual agricultural practices are becoming ever-more evident and as the weight of evidence builds for positive change, farmers around the world are starting to reassess the fundamental nature of farming itself.

Agriculture is a complex sector encompassing crop and livestock agriculture, forestry, aquaculture and other land use, as well as subsectors such as energy crop production for biofuels and waste-product-use for biogas, and in some cases biomass. Some forms of agriculture are far more polluting than others, although surprisingly, the tweaks needed to switch from carbon- (or nitrous-oxide-) emitting to either carbon-sequestering or carbon-negative techniques are already starting to be implemented today; and at a scale not before seen. Depending on how countries wish to adopt supportive policies (or commercial ‘carbon credit’ schemes) to further the carbon-mitigating and sequestering potential of land use is of vital importance to eventual negative emissions strategies — which may continue for centuries after the final oil well is sealed and the last natural gas pipeline switches to hydrogen.

In total, the AFOLU sector (agriculture, forestry and other land use) represents about 23% of global CO2-equivalent emissions, including nitrous oxide and methane. The largest share of this is attributable to deforestation (40%), closely followed by livestock farming. Almost double the overall global land surface area is pastureland (21%) in comparison to cropland (12%), meaning that in terms of emissions per unit of land area, livestock (mostly cattle and dairy cows, via enteric fermentation as well as manure) make up the vast majority of emissions. What this means is that relatively straightforward measures such as genetic selection and breeding, optimizing the animal feed mix and using feed additives and furthermore the widespread use of anaerobic digestion units can all significantly decrease the methane emissions from livestock.

Soil Carbon and Carbon Farming
Increasing the quantity of carbon held in soil (soil organic carbon or SOC) is seen by many to be one of the best ways to reduce or sequester agricultural emissions while at the same time addressing issues relating to the ongoing impacts of climate change such as droughts, flooding and reduced soil health brought on by the intensive use of chemical crop treatments, which eventually leads to soil degradation. While it is generally accepted that yields do not significantly increase with most common methods employed to increase soil carbon, the co-benefits mean that costs are reduced while the resilience of crops to adverse conditions improves dramatically.

To understand how and why so-called ‘regenerative farming’ is increasingly being considered to be so important, it can be helpful to examine how soil and crops interact. First of all, we know that plants absorb CO2 and convert this into sugars which they use to grow, and also to feed to soil biota through their roots. Normally, these soil biota ‘fix’ nitrogen from the air and package this nitrogen (as well as many other nutrients) so that it can be absorbed by the plant. In the natural world, another form of nitrogen comes in the form of ammonia which is found in urea from animals. However, within chemical agriculture, this nitrogen is often administered directly, and this can have a destructive effect on fragile soil webs and soil biota — in effect, similar to hydroponic farming but with the addition of rain and other conditions which gradually deplete the nutrients within the soil. Soil health is a complex subject, with many different types of soil found across the world. However, high levels of soil organic carbon are the basis of healthy soil, as this soil carbon harbours the soil biota that the plant needs, as well as storing water, and increased quantities of micronutrients.

In order to increase this soil carbon and thus soil health, many different practices may be implemented; however the most common are what are known as ‘no-till’ farming, cover-cropping (ensuring that soil is not left bare for extended periods), and applying mulch and other plant matter to soil so that the soil is fed and not overturned, where the carbon can decompose if it is left to the elements. These farming practices in reality represent minor changes in technique and are easily applied; while reducing the amount of labour, fuel, water and other inputs; making the practice of carbon farming prospectively implementable at a very large scale (40% of US cropland now employs some level of regenerative farming). For these reasons, France began championing its ‘4 per 1000’ initiative in 2015, which proposed that by increasing soil carbon stocks by 0.4% per year, agriculture would become a net negative emissions sector, contributing to a significant reduction in overall anthropogenic emissions. While this movement may have been slow to catch on in some regions (potentially due to the lobbying interests of large agricultural chemical companies), the value of soil health is becoming more and more understood. In fact, in the US a growing body of information and resources are being applied to the subject of soil health and soil carbon, and a growing number of farmers are starting to see the advantages of regenerative agriculture; to the point where not only are major companies offering farmers carbon credits for increased levels of soil carbon, but laws are now in place and ready to be implemented should a Democratic administration win the 2020 US presidency. Such is the confidence that soil carbon is an issue worthy of support and policy intervention that a bipartisan ‘Growing Climate Solutions Act 2020’ has been put to the senate, and offers a way of trading the carbon sequestered on either national or international trading platforms. Presidential candidate Joe Biden has taken this one step further under his ‘Plan for Rural America’, and has pledged to make the US agricultural sector the first in the world to achieve net-zero, in part by paying farmers for increased soil carbon. The concept also has significant commercial backing in the US, including a company named ‘Indigo Agriculture’ which operates internationally, and has a market capitalisation of $1.4 billion. The company offers a suite of tools to help farmers reduce crop inputs via satellite imagery, soil sampling, and also the use of novel crop treatments that are starting to replace conventional treatments in many regions as farmers begin to understand the negative consequences of chemical alternatives. In many ways, it has become obvious that conventional chemical farming methods are in flawed, and amount to an unwinnable arms race between different pests and various agrochemical products, as climate impacts such as drought and flooding become a perennial feature. In the US, recent flooding has shown that in those fields implementing no-till, cover-cropping and similar practices, annual yields were largely unaffected by torrential rains. In those fields not implementing these techniques, the land was unable to drain, and much of the nutrients within the soil were washed away; meaning that a year of revenue was lost, paid for in most cases by large insurance claims that are going to become less tenable as climate impacts increase in intensity. Also, for some invasive species and pests; no other method exists to counteract them, meaning soil health and the support of natural systems such as cover-cropping are the only realistic answer. In this way, the resilience of the system becomes more important than a number of years of exceptional yields.

Other component parts of the regenerative agriculture trend are often just conventional organic farming practices, although Indigo Agriculture have identified a set of tools which they focus on as a part of their commercial offering, which comes as a package where most aspects of the grower’s experience are taken care of. An important part of this package is offering tailored microbial seed coatings, which essentially provide plants with biofertilizers and biocontrols which boost crop growth by protecting crops symbiotically. The Indigo system also offers Indigo Transport, Indigo Marketplace, Indigo Atlas and Indigo Carbon among a host of features; with a focus on the farmer that encompasses precision farming techniques using satellite imagery among other services, and a carbon credit scheme linked to their ‘Terraton Initiative’. This initiative; while perhaps highly ambitious (1,000 gigatons of carbon sequestration via soil carbon) does succeed in highlighting the enormous potential to improve crop security and nutrition, while sequestering vast quantities of carbon. Biofertilizers, biofungicides and biocontrols are a fundamental component of this system, and many companies are now joining the ranks of those implementing these biological alternatives with unparalleled and award-winning results. Biofertilizers have been in use in Asia for centuries, however they have only started to become popular in Europe and the Americas very recently. Big names such as Monsanto and Danish company Novazymes have teamed up to offer a number of products, and many other collaborations have formed, such as Dupont and Taxon Biosciences. Other smaller companies such as Locus Ag are starting to win big prizes for their tailored Rhizolizer soil amendments for crops, citrus and vegetables; and Terradigm for pastures. In addition to increased crop yields, these products also greatly increase soil carbon, while also being self-propagating if undisturbed by chemical treatments, meaning they can be applied at large scale. The results are almost too good to be true, and have completely changed previous opinions about biofertilizers and biopesticides; which require specific storage conditions to maintain efficacy, and which has meant that shipped products have often fallen below expectations in the past. Like Indigo, Locus Ag are also selling carbon credits for those who sign up within a partnership scheme, highlighting the simple logic of storing carbon for money; by using a cheaper, more effective product. Endorsed by Forbes, the US DoE’s NREL among others, tailored biofertilizers such as those by Locus Ag, coupled with carbon farming, are likely to significantly reduce the impact of agricultural chemicals, as and when specific policy is implemented. In addition, very recently the multinational pharmaceutical and life sciences company Bayer (which bought Monsanto in a move towards health and agriculture) has implemented its own carbon credits system in the US and Brazil, with a view to expanding the system globally. When such big names are moving into regenerative agriculture and initiating systems that reward farmers for no-till farming, cover-cropping, and reduced fertilizer use — it is obvious that change is occurring within the agricultural world.

Precision agriculture and digital augmentation
Issues such as soil quality, water use, fertilizer use and transport costs in agriculture are starting to be tackled by the availability of specialised platforms and software that integrate information to minimise waste and produce high quality yields without the detrimental effects associated with conventional agricultural methods. These platforms, such as Granular, which is the world’s leading (mobile-centric) Farm Management Software, are also starting to integrate carbon accounting functionality, which will enable farmers to more accurately quantify how much carbon they are storing, and what the advantages of this stored carbon are. Initially, the software will integrate with the digital marketplace for CO2 designed by US start-up Nori; however, as larger players such as Indigo Ag and Bayer also start to recognise the value of turning agriculture into a net sink of carbon — potentially joining larger carbon pricing mechanisms (although ideally with caveats, as carbon sequestered in soil is not necessarily a permanent fix) — which in effect solve a range of issues, to a certain degree. Reducing fertilizer use, nitrous oxide emissions and transport fuel — as well as methane emissions from livestock — are all genuinely positive developments and account for a very large proportion of overall emissions within the sector.

The data provided by these commercial services is not confined to a few select companies however; and today there is a growing awareness of the need for integrated platforms that provide specialised satellite data and allow farmers to share information within an open-source way. One of these is a digital agriculture platform built by the Argentinian Farming Association (ACA); which supports 140 cooperatives and 50,000 farmers. Argentina is a major exporter, and a perfect test ground for organisations like the ACA. The system uses geospatial data analysis, machine learning and cloud computing using data from satellites and drones to provide real-time data to farmers, and ideally this award-winning system could stand as an example for other agricultural associations globally.

Another example of a digital platform is the French organic waste marketplace, connecting biogas producers with those with waste to sell; thus turning waste into the valuable commodity that it is. As one of the largest agricultural producers in Europe, France plans to replace a large proportion of its natural gas with biomethane, and the Organix® platform should expedite the efficient use of available waste streams within France and potentially elsewhere.

Biogas, biomass and biofuels
Already in China the government has capped the growth of the chemical crop treatment industry, while also mandating the use of anaerobic digestion in livestock and poultry farms to produce biologically-based fertilizer. This is significant, because without some form of government control, pesticides and fertilizers will continue to degrade soils, and the industry — just like the fossil fuel industry — will keep trying to extract higher profits. As a second prong in the fight to reduce emissions, biogas production via anaerobic digestion offers an entire suite of advantages for everybody involved. Biogas production is expanding rapidly worldwide as technology and know-how enable farmers to produce multiple revenue streams, even on small family-sized farms which make up 75% of the world’s agricultural land. In Europe, meeting targets for biogas mean that some countries will see an exponential increase in production, as well as the services required to effectively utilise waste agricultural products. Essentially, biogas production involves the transport and collection of waste products to be fed to an AD unit (anaerobic digester), where bacteria break down plant material to form methane, which can be piped into a biomethane gas network, as well as producing a rich substrate which can be pelletised or liquidised and sold as organic fertilizer. The advantages of doing this are diverse; first, biogas displaces fossil gas, and can be used in niche applications where pipeline quality or specific applications cannot accept hydrogen; second, it is reducing the need for chemical fertilizer — this increases soil carbon and improves soil health and resilience to drought and flooding; third, the substrate fertilizer produced may be categorised as negative emissions — which carries with it the potential for monetisation within a carbon pricing system; fourth, this could be further augmented by converting the methane produced into biohydrogen, thus providing fuel for vehicles and machinery, while also offering another form of more permanent and secure negative emissions as the CO2 is either piped underground or converted to solid carbon; fifth, because chemical crop treatments are being avoided, emissions from ammonia production and the decomposition of unused nitrogen (N2O) are negated; pollution via run-off is eliminated, and furthermore, biofertilizers and biocontrols are more effective as they are not being adversely affected.

To underline the correct use and application of biogas production in combination with no-till, cover-cropping and other activities; which both produce a revenue stream and increase the resilience and nutrient value of the soil; the Italian biogas organisation formulated the precise methodology which they have titled ‘Biogasdoneright® ’, and which as they explain is sustainable, low cost and reliable — while also providing BECCS (bio-energy carbon capture system) which can be applied everywhere.

If we look at different targets that exist for biogas, it’s possible to see what a dramatic effect widespread biogas production is likely to have. For example, NREL predict that biogas production could replace 15% of US natural gas used for heating and cooking. In addition to this, SoCalGas and Opus 12 are trialling a single-step process that converts the carbon dioxide fraction of biogas to methane — doubling the methane output — via the use of electricity. Other methods exist to increase the biomethane content of biogas; for example such as via the ‘Electrochaea’ process which uses a biocatalyst within an AD unit; however, an electrochemical pathway may have greater potential at higher volumes. In this way biomethane or renewable natural gas (RNG) may be a less expensive option in some areas than the cost of converting residential areas to full electrification, or to hydrogen — although critics will point to downstream leaks within gas networks as perhaps being a reason to make more of an effort to move away from methane; or convert the methane to hydrogen.

In Europe, approximately 4% of the total gas demand is now being met by biomethane, and the potential as cited in various reports to date is between 15–25% of current demand; or up to 50% of future demand depending on the need for gas heating in 2050, and the replacement of gas by electrification and heat pumps (as outlined in the ‘Gas for Climate’ report). The latest version of this report estimates that gas consumption will fall from about 5,000TWh in 2019 to approximately 2,900TWh in 2050 — however these estimates do swing wildly over the years and in this case, for instance, biomethane use in heavy transport is expected to increase by a factor of 10–15 (whereas hydrogen plays a much smaller role). This underlines the link between some consultancies’ projections and the use of biofuels for transport (eg, ‘2030 Transport Decarbonisation Options’ report by Navigant, 2019). The utilisation of biofuels (rather than biomethane) is controversial, as biofuel production almost always competes directly with forestry or food production, as well as generally negatively impacting soil health.

These issues bring into question the responsible use of land, and what realistic demands from domestic biomass resources can be made. In Europe, large quantities of solid biomass (wood) are imported each year; mostly from the US, and this wood is burnt in replacement of coal in some countries. The prospect of capturing the emissions released from thermal biomass power plants offers the potential for negative emissions; and indeed the Drax plant in the UK will be piping its CO2 offshore, as well as with other industrial users.

Reducing livestock emissions
In terms of livestock and dairy farming, which is where the majority of emissions are produced, other options besides biogas production are available. The first is selective breeding, as well as dietary supplements to reduce methane production from the enteric fermentation process. This is now being trialled at scale, and certain fodder supplements such as specific strains of seaweed have been shown to reduce methane production by 90% and more at high doses. Further to this, Burger King are now marketing a new ‘low-methane’ burger, which is likely to become standard within their product range, and potentially throughout the industry as quality standards are applied. In countries where animals are bred intensively, many of these measures may be applied to great effect. More tests and trials are necessary, but the logic that methane is wasted energy implies that a commercial advantage exists for farmers supplementing animal feed in this way — which could be further advantaged if agriculture was a part of an international carbon pricing system.

Much of the world’s protein is currently met by fish, and this is likely to remain the case as now over 50% of all fish consumption is farmed rather than caught in the wild; which may in future somewhat reduce pressure on intensive cattle farming. Climate impacts are likely to increase the cost of meat (especially emissions-intensive meat), and as well as this, as population growth declines and tastes change among a growing elderly population, this may also contribute to less growth in the market for emissions-intensive livestock farming. Population growth is obviously a very significant factor, although as more data comes in and reports are collated, projections from the 2000’s citing 10.8 billion by 2100 may in fact turn out to be substantially higher than the reality. A recent report sees the continuation of observable trends, where the global population peaks in 2064, and start to decline; reaching about 8.8 billion by 2100. This means a much larger elderly demographic, which is already being expected in many developed countries, and overall much less pressure on the planet’s ability to provide adequate nutrition.

Indeed, one set of options which may start to become more fashionable as temperatures rise and the burden on agricultural systems increases, are meat substitutes; which today encompass a very wide range of products, and in many cases taste identical to the original. Everything from Tuna to Bacon now has a substitute, and some are even earning awards such as Sweden’s Oumph! range of smoked ribs, burgers and mince; Burger King’s identically-tasting ‘Rebel Whopper’, as well as vegan chicken, pizzas and other foods now available from a range of multinational and local brands. Various reports highlight the cost declines of lab-grown meat, such as Eat Just’s ‘chicken bites’ which are now available in Singapore, and are nutritionally identical to the real thing. It is expected that lab-grown meat will replace a large percentage of meat products currently consumed once the technology becomes mainstream, in some regions.

Developing the potential for sequestering carbon at scale
Looking further ahead towards the end of the century, a number of factors may combine to expedite the development of specific technologies in the hope of sequestering carbon on a greater scale, while also providing fuel or fertilizer, as land-based biomass resources are increasingly in short supply. Uppermost within the range of options is the widespread development of aquaculture, which will supply biomass for biomethane production; nutrient-rich substrate for recovering land lost to desertification, and healthy environments for fish farming in the deep ocean, in combination with ubiquitous wind farms.

Reading the IPCC Assessment Reports and others, a central feature of these reports is the necessity to start dragging emissions not just to zero, but below; and land-based agricultural practices (such as the increase of SOC and BECCS using land-based biomass) may not provide the negative emissions necessary. In fact, much of the IPCCs reporting (mostly within 2019’s Special Report on Climate Change and Land) shows that while around 8–10 GT CO2 could be sequestered via forestry, soil carbon and BECCs each, these high figures sometimes rely on extreme measures such as reforesting large areas of grazing lands. A slightly more realistic figure may be around 1 GT CO2 each, and even here, these methodologies require that no increase in deforestation continues, and that wildfires and other disasters are somehow avoided. I believe that 1–2 GT CO2 via soil carbon is realistic, but will have to be treated as a contingency measure before more permanent CO2 storage is implemented at scale.

As the IPCC reports state, carbon dioxide removal (CDR)/negative emissions technologies (NETs) are considered to be an intrinsic component mitigating what many perceive to be the almost inescapable onset of positive feedbacks; where the climate continues to warm for a range of reasons even after humanity is no longer burning fossil fuels. In the graph below, this fact is represented by the 'Net emissions' line reaching approximately 3 GT below zero in 2100.

As we can see, for a greater than 50% chance of 1.5°C by 2100, 4 GT CO2 removal via AFOLU is required, and 3GT CO2 removal via BECCS. However, this estimate presupposes that we cannot reach zero total emissions, and therefore this CDR is required to offset existing emissions. These emissions include nitrous oxide and methane. Essentially, if closer to zero was achieved from methane and nitrous oxide; mostly by adjusting ruminant diets and reducing fertilizer use as well as other factors, the only reduction required to keep the planet stable is approximately 3–5 GT CO2 per year.

As we have seen, soil carbon has great potential to both increase crop resilience and (temporarily) sequester atmospheric CO2. I estimate this to be approximately 2 GT CO2 if carbon pricing were to be implemented globally. The second most effective means of storing carbon at scale is most likely the use of BECCS (Bio-Energy with Carbon Capture and Storage) — or, as recently outlined in a new report ; BiCRs (Biomass Carbon Removal and Storage). This is almost the same as BECCS although the emphasis in this case is just on carbon removal rather than energy production, because within the context of an effective carbon pricing system, the value of carbon removal may be higher than the value of the energy produced. In my estimation, I think it is safe to say they are almost the same thing, and indeed the recommendations arrived at within the report outline a number of specific technologies which nearly all contain an energy-related value stream.

First amongst these is the use of waste biomass in order to produce biomethane, which is very much a large part of many countries roadmaps to net zero. The report is careful to exclude all forms of biomass production that could cause environmental damage or negative impacts on food security. Using such sources, with a focus initially on biomass waste (including municipal solid waste, agricultural waste, forest waste and sewage), the report finds that between 2.5–5 GT CO2 are likely to be possible by 2100, not including soil carbon which is considered a less long-term form of carbon storage. Putting these together for the purpose of argument, we can see that if a more rigorous zero carbon pathway is achieved, the planet may not be too far from a point of climatic stability, sequestering between 3–5 GT CO2 per year.

Other specific components highlighted include direct biomass to hydrogen conversion via fast-pyrolysis to produce solid carbonate, which is a technology that could scale rapidly by 2050, being both cost effective and practical, in addition to traditional biomethane production using anaerobic digesters. However, the advantage of AD units is in the production of fertilizer, so perhaps both technologies will find applications. The report also specifically mentions macroalgae, once the technologies have matured and sufficient carbon pricing systems ensure profitability.

Already, 1,900 sq km of the ocean are being farmed for macroalgae (seaweed), which is the fastest means of reducing atmospheric carbon today (growing up to 60cm per day), while also providing fuel and fertilizer in unlimited quantity. Per hectare, seaweed sequesters seven times the quantity of CO2 as land-based lignocellulosic biomass, while not competing with food production or requiring fertilizer, fresh water or other inputs. It should also be reiterated that seaweed has an approximately 2 GT potential to reduce methane emissions from livestock farming.

Looking at the potential for seaweed that currently exists, Dr Antoine De Ramon N’Yuerte from the University of the South Pacific and his colleagues have calculated that using seaweed for methane production and consequently storing the carbon produced via bio-energy carbon capture, vast quantities of CO2 could be sequestered . His calculations may also include the organic substrate produced within AD units, although this is not referenced. Ultimately, Dr N’Yuerte has calculated that 53 billion tons of CO2 could be captured this way per year, using 9% of the ocean’s surface. However, if the volume required only reached 3 GT CO2 per year, this represents only 0.509% of the ocean’s surface . In total, this equals 1.08 million sq km; which is surprisingly small, being approximately equal to 70% of the Mediterranean, or three times the North Sea. Because most of the North Sea will be filled with wind turbines by 2100, this does not appear to be impossible. In effect, to achieve 3 GT CO2 mitigation per year, 45 times the sea surface area currently producing seaweed commercially would need to be farmed.

Macroalgae production at scale is just starting to be explored in Europe and North America, as the need for valuable biomass grows. Regarding what may be a major industry by 2050, we can understand how specific strains are grown on ropes, which are then placed in water, 10–20m below the surface. This seaweed can then be dragged from lines to be fed into large floating biodigesters or fast-pyrolysis units. The resulting hydrogen is piped ashore, the CO2 is piped into deep saline aquifers (or stored as carbonate in the case of pyrolysis), and the substrate (fertilizer) dried or sold in liquid form.

In addition, fish farms operating above these vast banks of seaweed can be better farmed in the oxygenated water produced, while also facilitating healthier plant growth via the ammonia produced by fish.
The possibilities in this regard are enormous, and indeed humanity may come to rely on aquaculture and related techniques to a much greater extent than it does now, as land is lost to desertification. By using biomass as fertilizer at scale, this could dramatically reduce the production of N20 emissions, which represents another 1.5 GT of emissions globally. Additionally, nitrogen and phosphorus are removed from coastal waters, creating healthier conditions for sea life.

Many countries have only just recognised the value of this valuable biomass product, and are starting to invest. For example, Australia has just spent $100 million launching its own seaweed sector, and many countries are turning to seaweed production as a means to escape the effects of the pandemic-enduced recession. As an example of the ambition now focused on seaweed, a report titled Seaweed Revolution: A manifesto for a sustainable future has recently been drawn up by the UN Global Compact and Lloyds Register Foundation. As the manifesto states:

“Going forward, we can scale up this industry to deliver safer and healthier food, renewable biofuel, low-carbon feed, as well as capturing and storing carbon dioxide to limit climate change, while also creating new sources of revenue to alleviate poverty in coastal communities. ”

Considering the vast quantities of biomass, fuel and carbon capture required, it is certainly fitting that a global initiative has been formed, and plans could soon be underway to implement macroalgae production at scale.