Feeding the soil and avoiding fossil fuels is the Holy Grail of sustainable farming. Techno-solutions aside, this will entail working with nature by mimicking nature – and harnessing the capabilities of ruminants. In the final installment of this series, Stuart Meikle outlines solutions for fossil fuel-free farming. The full series will be available as a PDF.
Targeting Fossil Fuel-Free Plant Nutrition
To recap Part Three, rumen-living microbes accelerate the degradation of organic matter to produce energy that is utilized by the ruminant. Outside the rumen that biomass would break down over a period of months or years to CO2 and, some to a lesser extent, to CH4. That plant degradation would happen. In nature, rumen degradation also symbiotically accelerates the cycling of nutrients back to growing plants.
By harnessing the capabilities of the ruminant to speed the degradation, the farmer utilizes a non fossil fuel-based energy source to produce food, several other biodegradable materials, and to build soil fertility to feed succeeding crops.
In the latter case, it is what will enable the farmer to find the Holy Grail, which is fossil fuel-free, non-polluting plant nutrition.
Fossil fuel-free plant nutrition
As far as artificial plant nutrition is concerned, what will have a constraining impact first: will it be the availability of fossil fuels for their manufacturing and/or mining, or regulation to control the pollution and emissions they cause? Either way, the production of food, fibre and biofuel relies on fossil fuels, and a rethink is now required.
Without access to artificial fertilizers to the same degree as in the past, how is agriculture to provide food, fibres and biofuels for several billion people? And that is without considering climate change or the biodiversity crisis.
Techno-solutions apart, it will be about evolving agricultural systems that work with nature by mimicking nature.
Nature can provide abundance, but whether nature can do so to meet the demands of humans is the question. However effective the agricultural systems of the future are, the nutrient offtake required by humans is vast. It is likely that reversing out of fossil fuel-derived fertilizer dependency will place more, not less, pressure on land.
Within the land sharing vs land sparing debate, are we even starting from the right baseline? Is intensification of less land truly realistic if plant nutrient availability and fertilizer emissions and pollution are fully accounted for? Yes, technology can help, but if nutrient losses are now about 70% to 80%, there is a long way to go to zero.
Is the more realistic scenario one where, 20 years on, agriculture is still using similar areas, albeit maybe with some withdrawal from some upland areas? It will be about utilizing land to access plant nutrients naturally and that will mean working in tune with nature. It will be about rotational agriculture to build soil fertility, and thus arable land will include fertility-building, often grazed, crops. Where the emphasis is more upon nature, it will be about highly diverse meadows and woodland pastures. And to speculate, these pasture-based systems will be a necessity as they can provide fossil fuel-free plant nutrition and, thus, foods, plus deliver for biodiversity.
Fundamental to all agricultural systems will be soil carbon and humus building to rebuild the biological systems that can naturally create abundance. It will be about soils-first farming. As there is a causal link between the use of artificial nitrogen fertilizers and soil carbon loss, is there a lack of reality about thinking that intensification of cropped land is a solution? We should be asking if such an approach will only increase our dependency on the use of artificial fertilizers and all they entail, including the full cost of pollution and their various GHG emissions.
Evaluating agricultural systems
In recent years there has been a massive emphasis placed upon carbon emissions from agriculture. Inevitably the reaction has been to base agricultural system performance evaluation upon carbon emissions. This has likely meant that greater emphasis has been placed upon carbon, although all plant life draws its carbon from the atmosphere.
Meanwhile less has been placed upon nitrogen whereas it could be argued that the complex of nitrogen-linked issues of nitrates, ammonia and nitrous oxide is an extensive, longer lasting problem. Addressing it is also a more significant challenge for an agricultural sector highly dependent on artificial nitrogen to maintain production.
While not downplaying the potential for swift climate change mitigation from well-aimed methane reductions, it is possible that the emphasis on carbon has had a detrimental effect on the overall environment.
Even when using carbon as a performance indicator, it is important to choose the right one. Is valuing food by its calorie content appropriate, or should a wider measure of nutrient density be used, albeit it may be more complex? And evaluation should not be based upon the quantity of data collected when comparing farming systems; it is about the in-depth analysis and understanding of indicative systems. It is the understanding that counts. And could there even be an inverse relationship between the data volume and the acquired knowledge?
There is a myriad of farming issues to address at present, the entirety of which may not be addressed effectively if the carbon footprint is the initial indicator of performance. It is possible, even probable, that the best carbon-farming systems will be those where carbon performance is the cumulative result of the many system changes needed for a system to mimic and work with nature. A few other key performance indicators (KPIs) are listed below:
- fertilizer (especially nitrogen and phosphate) use per land unit or per unit of food nutrient
- plant nutrient losses (which is more complicated) per land unit or per unit of food nutrient
- fossil-fuel usage at all points within the system per unit of land or per unit of food nutrient
- antimicrobial usage per unit of food produced or, still preferably, food nutrients produced
- offtake crops (typically grains) fed to farmed animals per head or food nutrients produced
- soil carbon percentage and soil volume to indicate system health (not sequestered carbon)
Yes, these measures are far more complicated than carbon emissions and that is why they should be used on an indicative systems basis. There is a vast amount of data being collected on carbon emissions from agriculture, but that data is collated using rules designed to accommodate that collation. Thus, they can be very broad-brush and over-simplified. It is unlikely that they will be suitable for evaluating complex working-with-nature systems.
With the last KPI, it should be noted that soil carbon building is not about offsetting fossil fuel-derived emissions, it is about creating the plant-growing environment that will allow the reduction (and maybe removal) of fossil fuel-derived artificial fertilizers every year from here on in, ad infinitum.
Restoring the soil habitat is the equivalent of giving a person a fishing rod instead of a fish. Soil carbon is about the long-term offset of GHG emanating from fossil fuel-based fertilizers. It is also about the cost of mitigating the impacts of their residuals. It is also about N2O and ammonia reductions. These are the main reasons for soil carbon building rather than carbon drawdown alone.
Grazing-ruminant methane is a cost that will be incurred to rebuild broadacre soil carbon and to maintain that soil carbon given that offtake cropping itself frequently degrades soil carbon. Their manure is also a vital tool in transferring plant nutrients between farmed crops, be that in terms or time and/or space. These are essential functions for food systems. They are also vital for farmland biodiversity recovery. Such will, however, not happen if grazing ruminants have already been ruled out by carbon accounting rules based assessment. Hence, when placed and assessed in the right context, ruminant methane is seen to underwrite sustainable food production.
A fossil fuel-free farming focus
The term ‘fossil fuel-free’ should be primarily considered in two contexts in agriculture. It is about the reduction in direct fossil fuel usage for power and its use to manufacture, mine, deliver and apply artificial fertilizers. Fossil fuel-free may also be applied to specific fossil fuel-based inputs like plastics and pharmaceutical and pesticide manufacture. Where fossil fuel fertilizers are used there is also the associated costs of N and P pollution removal.
At present, producing fossil fuel-free food to feed billions of urban people is a pipedream. By the end of the century people will look back and realize that it was not and that targeting such was just another step in the evolution of human civilization. It will result from the careful use of genuinely renewable energy (i.e., not that associated with crop offtake) to replace fossil fuels and the use of food systems powered mainly by solar energy.
At the forefront of this agricultural revolution will be the focus on the plants that can be fed by the soil biome. It will be about feeding the soil to feed the plants. And offtake crops will be fed by the plants that can operate symbiotically with the soil biome and leave a fertility residual for the next crop. Increasingly, one can expect that polycropping will enable the symbiotic plant-to-plant relationships to work simultaneously, not consecutively.
Is it purely coincidental that focusing on a plant diversity that can secure its own nutrients from the atmosphere and soil profile is to focus upon the soil biome and its interaction with plants? Or that, for that to happen, the focus must be on building and maintaining the soil habitat and carbon? And that itself needs grazing herbivores, and especially when the farmer is seeking to accelerate natural degradation, as indeed must happen.
This is all about relying on the systems evolved by nature, but they cannot happen if one key part is missing. When it is, as in the past, fossil fuel-based – or before that, manual, human energy – is used to plug the gap. Trying to design a food system by deliberately removing one of the fundamental components provided by nature is to invite failure.
A consequence of the above is soil carbon building and when this occurs at depth and within farming systems designed to safeguard it, carbon drawdown will occur. To what degree will vary with farm, soil and system. It is not easy to quantify or measure. Further, the importance of protecting soil carbon will mean ensuring that soils are protected by vegetative cover and that will improve the local ecosystem.
The emphasis on atmospheric and soil-profile nutrient sourcing for plants naturally will also reduce the vast nutrient leakage that already occurs (Nature’s systems would simply not have evolved to tolerate nutrient loss; nature does not function that way). Those lost nutrients have a fossil-fuel footprint and emit and pollute.
All of this is beneficial to the fight against climate change, but just how much of this actually falls within the bounds of carbon accounting methodology?
Fossil fuel-free product creation
In the first instance this will be based upon harvesting those plants that can feed themselves. A few pulse crops are, at least from a nitrogen perspective, capable of feeding themselves. As said, others will emerge through the development of polycropping systems where symbiotic relationships can enable the whole to be self-sustaining in terms of plant-nutrient access. By definition, their management will be far more complicated than monocrops.
Further, where soil aggregation is allowed to occur around plant roots, anaerobic ‘pockets’ are formed that allow nitrogen-fixing bacteria to drawdown atmospheric nitrogen. This is exchanged for root-exudated carbohydrates in a symbiotic relationship with the growing plant. The bacteria themselves obtain their energy from the sun via the photosynthetic activity of the plant. A similar relationship exists between mycorrhizal fungi and plants with the exchange being ‘liquid carbon’ for soil-profile-held nutrients. These are natural, fundamental relationships.
The important factor is crop permanence and much reduced (or zero) tillage. This contradicts the situation where so many current human offtake crops require tillage, are non-permanent and contradict the soil habitat stability needs of the naturally functioning nutrient-sourcing and transfer systems. Into the future, our sustainable food systems must be built upon soil habitat, and thus crop permanence. With the scale of the human population’s food, fibre and biofuel needs, we cannot forsake opportunities to harvest these crops. And, incidentally, these crops are also more resilient in a changing climate, including one where drought becomes more commonplace.
Grazing herbivores, and to a lesser degree, omnivores play a key role in allowing fertility building crops to provide for succeeding fertility consuming crops. Many of our mainstream food crops fall into this latter category. Such is the importance of the grazing animal in bridging the fertility succession gap, it is possible that grazing animals are required in food systems even if we choose not to harvest their products. Such an approach would certainly reduce the total productive capacity of the system, but the point illustrates the importance of grazing herbivores.
Instead, as said earlier, animal-free growing systems are possible, but they will probably be unable to deliver the broadacre scale needed to feed several billion people. They will, nonetheless, be a key food system component.
Lucerne (alfalfa), sainfoin, trefoils and vetches will be the key agricultural crops, at least in temperate climates. It is not by chance that they are all capable of fixing their own nitrogen. Even then, the plant diversity within a pasture, be it permanent or rotational, needs to be far greater to include plants that are adapted to sourcing other nutrients from the soil profile, some of which are not in an accessible form to many crops. These typically deep-rooting herbs also enhance the pasture’s drought tolerance.
Plant diversity is also likely to make available plants with medicinal properties, while others have anthelmintic capabilities. The latter are likely to become invaluable as resistance to wormers rise and the knowledge of their residuals on soil life becomes better known.
As stated before, there will be increasing use of companion planting and polycropping. In the latter mechanical separation techniques will be important, and that will also mean mixed crops that can be harvested together. It is not by chance that vetch and oats (or barley) have historically been grown together. In some climates they can be harvested together and separated; in others their use may be limited to harvesting them green for forage.
Hence, we have a situation whereby many of the crop plants that can sustain themselves (but still most likely within a diversity) can only directly be utilized by herbivores. The human simply has not evolved the digestive tracts to consume them. These crops are to be found in permanent pastures or fertility building herbal leys or in cover crops used to protect soils and/or build fertility within arable cropping rotations. On a broadacre farming scale, these crops have to be grown and given the size of the human population, somehow indirectly utilized.
Thus, if we are to live without our reliance on fossil fuels, harvesting herbivores for meat, milk, fibres and their many by-products (the value of which is typically not considered in too narrow evaluations of sustainable food systems). When it comes to the ‘eat less meat but better’ mantra, the better must start with questions over the farming system’s reliance on fossil fuels and especially artificial fertilizers that are mined or manufactured using fossil fuels. This is a far better indicator of performance than using overly simplistic carbon emissions counting.
Fossil fuel-free power for agriculture
The herbivore up until 100 years ago powered agriculture. In many locations it still does. Horses, asses, donkeys, oxen and water buffalo all still provide tractive power for cultivation and transport. And, unlike the internal combustion engine they only require biomass to feed them. They are also finally biodegradable. As the soils-first approach to farming becomes the norm, there may increasingly be niches for their use again. Less-cultivation tillage will mean less power is needed and some re-evaluation of techniques will follow. It is, however, inevitable that mobile power will be needed, and the engine-power source-options include electricity and biomethane gas.
Biomethane can be used as a direct engine fuel or via conversion to electricity. Sadly, its capture from animals directly is likely to be limited so it will be about using slurry and farmyard manure as a feedstock for anaerobic digestion plants. Crucially, as the feedstock includes valuable plant nutrients, the residuals from the process must be recycled back to the land. There are, however, numerous system questions to ask, such as:
- are (aerobic) composting barns a better option altogether when winter housing is a necessity? Is the product useable by the horticultural sector? Are there animal welfare benefits? Are there also housing cost benefits?
- can forage plants as a direct feedstock for anaerobic digesters be justified if they are seen as nutrient offtake crops? It is not just about carbon emissions; it is about cycling all plant nutrients. Can the feedstock nutrient offtake be balanced by nutrient return? Can the whole be seen as a closed-loop agricultural power source?
- should energy created with agricultural feedstocks only be viewed as energy to power agriculture and food?
- as it is essential to use food waste and below food-grade produce, should this go to anaerobic digestion? Or should it go to feed monogastric pigs and poultry first? The systems can be circular, but to what degree do they culminate in plant nutrients being returned to the land? How much energy is needed to close the circle?
An important overall question for all biofuels is whether they can be produced without consuming artificial plant nutrients. It is an issue for food, and it will be for fibres, but it is a major issue for biofuels. Hence, is it possible for the plants utilized for both biofuels and biomass (including that used for biomaterials like bioplastics) to regenerate the plant nutrients used naturally? Or are they also fossil fuel-dependent and, thus, an illusion?
Fossil fuel-free service provision
As we move into an era where fossil fuel usage is scrutinized and there is a greater reliance on renewable energy, land management by herbivores will be a valuable tool. In some cases, it may be a direct choice between the use of fossil fuels and CH4 emissions (as the by-product of energy creation by rumen-living microbial life). The situations are varied, from amenity land management, to clearing leaf debris to prevent forest fires, to creating organic matter to reverse desertification of soils. It is again about looking at ruminants as a strategic resource.
High Nature Value land management
There are many examples to be found where grazing herbivores have been found to be the best tool to manage land recognized as being of high nature value. Often this is a direct alternative to mechanical or manual methods. With the former, the methane produced by the grazing animal should be considered as a substitution for fossil fuels. Further, there will also be food and fibres produced if the choice is made to harvest them. It may not be. It may be that the conservation management services are sufficient in their own right to justify the CH4 produced.
It should be noted that the HNV land area is not fixed. In some cases, land use and/or management changes may enhance the value enough for it to become considered HNV land. To achieve such status, the grazing herbivore may be the most effective tool. This will also not be limited to creating HNV land that is then reserved for nature.
The United Kingdom has lost 97% of its HNV wildflower meadows since the ploughing-up campaigns of World War Two. This was to harvest their stored soil fertility. They did not return as artificial fertilizers meant that they could be maintained as arable land or ‘improved’ as pastures with newly bred, productive grasses (albeit they relied on artificial fertilizers). The misnomer is now that wildflower meadows need poor soils and are not, when established, agriculturally productive. The remnants are now just found on poor soils as they were unsuitable to tillage or ‘improvement’. Plant diversity and the soil biome does not function well when artificial fertilizers are used so there is the belief that soil fertility is the enemy of ‘wildflower meadows’, whereas it may be necessary for the soil to go through a ‘detox’ phase before the soil biome and plant diversity function effectively. Anyone familiar with the meadows of Transylvania will know that plant biodiversity and soil fertility go together to create abundance. We have just lost the knowledge to recognize such and to manage wildflower meadows to do so.
High Cultural Value land management
There are landscapes that have become iconic and culturally valuable. Often, they now have tourism value. This may, nonetheless, be a transitory situation with perceptions changing over time. In the meantime, some land can be designated as of high cultural value with society choosing to see it managed accordingly. Across the HCV land spectrum, techniques will vary with some requiring energy-using mechanical methods (they may transition away from fossil fuels to renewables) while others will use grazing animals, with CH4 substituting for fossil fuels.
Carbon sequestration and its storage
One will not be able to avoid the term carbon farming in the coming years and there will be a suite of carbon related activities linked to farming. Cultivation loses carbon while (some) pasture-farming can restore it is a simple message. But Conservation Agriculture is now providing many husbandry techniques to protect tilled-soil carbon while some grazing and/or fertilization approaches can lose carbon from grassland. It is a complex issue, and such is reflected in the often-held view that if it cannot be accurately measured it cannot be included in the carbon assessment of farming (carbon farming or otherwise). That is not a useful message to send to a critical land use sector when it comes to identifying sustainable food systems, including those that can also significantly contribute to planetary ecosystem recovery via the restoration and then the management of degraded soils.
The body of evidence around building and protecting soil carbon is still evolving as, for decades, ‘Soils’ was the Cinderella of agriculture. Soil biome feeding plants was not considered an essential subject when we had abundant artificial fertilizers and rather less knowledge of the consequences of using them. Instead, what has evolved is a knowledge base created by a largely informal network of farmers, researchers and advisors. It is possibly stronger for its diversity. Such is the imperative of the climate crisis, it is likely that this knowledge will move into mainstream agriculture, while formal research plays catch-up. It is a situation that will make it difficult to reward farmers for carbon capture. It should, however, be noted that such is a secondary activity; the priority must be for farmers to build resilient farming businesses, and that will itself drive their desire to capture carbon.
It is likely that carbon farming that involves stable carbon storage at depth will need the symbiotic soil biome /plant/grazing animal combination to work effectively. It is probable that targeting such functionality will also mean the minimization of the shocks to system that come from using artificial fertilizers and pesticides and the residues from pharmaceutical products. Minimal cultivation and cover crops will be necessary to protect that soil carbon during offtake cropping periods. Within broadacre agriculture, at several points, ruminants will be an essential, productive tool. They may emit CH4, but this must be balanced against their carbon-farming role.
Biodegradable ruminant products
The ruminant animal, whether domesticated or not, has provided humankind with a source of fibres since pre-history. At the point where they are a raw material for processing, they can be fossil fuel-free. Processing aside, at this point they must be compared to functionally-comparable fossil fuel-based fibres. The former utilizes fully biodegradable methane for their production (albeit with an atmospheric degradation time lag), while the latter uses fossil fuels. The former is biodegradable with their carbon being returned to the atmosphere via aerobic or anaerobic degradation, depending on whether that degradation takes place in the presence of oxygen or not.
If, however, that degradation occurs within the anaerobic conditions of a landfill, that carbon will first become methane and then, only later, CO2. Such will occur with the disposal of both plant-based and animal-based fibres.
The half-life of non-organic, synthetic, fossil fuel-based fibres may be hundreds of years with all that such entails. They may also create microplastic pollution during use (for instance, when laundered). Such microplastics may also render sewage and municipal compost unusable for plant production, thus incurring the loss of those plant nutrients to agriculture. Their replacement will also have to rely on natural regeneration without fossil fuels. The cost of synthetic fibres can be multiple and often go well beyond the ‘they are not biodegradable’ issue.
Finally, and frequently overlooked, the fibres produced from ruminants may sequester carbon for many decades. Wool and leather may have a longer fixed-carbon life than say coppiced timber used for biomass or softwoods turned into pallets and packaging. These are yet more factors to consider when evaluating agricultural systems.
Farming bounded by biological boundaries
This essay, including its earlier ‘soil-carbon primer’, covers the complex issue of how to create the sustainable agricultural systems that can work within the biological boundaries of the Planet. Such can be simplified to a degree, but any simplification is fraught with dangers. And such has happened to fit agricultural complexity into a carbon-based accounting system. Farming is not all about carbon: it is about much, much more. It is also not just about climate change; it is not even just about the biodiversity crisis – it is about a very great deal more.
The objective of the essay has been to demonstrate this, but also to show that there are relatively simple solutions to complex problems, once we start to understand how Nature can function to deliver our needs.
Plant nutrition sourcing and management in its totality is the central pillar to future sustainable-farming thinking and delivering nutrients regeneratively must drive our choices. And, like it or not, grazing ruminants with their methane-emitting power source are an integral part of the soil biome/plant diversity/herbivore nexus that Nature has evolved to manage grassland (albeit now converted to arable) and woodland-pasture ecosystems.
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