A proposal to rethink agriculture in the climate calculations

Per Frankelius

First published: 13 May 2020

Článek převzatý z https://doi.org/10.1002/agj2.20286

Abstract

According to the Intergovernmental Panel on Climate Change (IPCC), agriculture is a main source of negative greenhouse gases. The calculations are based on empirical facts but also, like all research, on certain perspectives or paradigms including assumptions and subjective choices of system boundaries for analysis. Greenhouse gases in relation to agriculture are often presented in diagrams showing, for example, arrows of emissions from soil, cattle, tractors, and manure storage. However, the fundament of agriculture is the photosynthesis. Carbon dioxide (CO₂) is caught by crops that, in turn, produce oxygen (O₂) and at the same time binds carbon (C) in roots and shoots. One part of this C transforms into soil organic C, and that is sometimes discussed in research, the public debate, and by IPCC. But the main part transforms into harvested crops, that is, cereals like wheat (Triticum aestivum L.), and other carbohydrate products like pea (Pisum sativum L.) or oilseed. This last-mentioned photosynthesis effect is not, in the IPCC calculations, considered as a positive climate contribution from the agricultural sector. The consequence of this might be that policymakers will not understand the whole picture of agriculture in relation to climate effects; and therefore make decisions that affect food production, climate change, and biodiversity in a not optimal way from a holistic sustainability viewpoint.

·  IPCC

·  Intergovernmental Panel on Climate Change

1 INTRODUCTION

The year 2020 might be remembered mostly for the coronavirus pandemic. But when observers in January 2020 reflected back on the year 2019 many concluded that climate concern had been one of the main issues in research and public debate. One example of this is that the Time Magazine chose the then 16-yr-old Swedish climate activist Greta Thunberg as “person of the year” and had a photo of her on the front page of the 23–31 December issue.

During recent years an increasing stream of research has been published on climate effects in relation to different sectors, not the least agriculture. One example is studies on greenhouse gas emissions and C footprint in relation to specific agricultural methods on specific types of soils in specific climate zones (e.g., Wang et al., 2020). Another example is studies on greenhouse effects derived from manure composting (e.g., Bai et al., 2020).

So, the climate discussion in society is, fortunately, intensive, and decision makers, who for example want to understand how different sectors affect the climate through greenhouse gases, try to interpret the huge amounts of information on the subject. Unfortunately, there are reasons to believe a paradigm-related skewness has made a foothold in policy-related research that also is mirrored in the public debate. It is about the climate effects in relation to agricultural production of food, fibers, and fuel.

The referred calculations and visual presentations are based on empirical facts but also, like all research, on certain thought styles (Fleck, 1935), assumptions (Polanyi, 1958), or paradigms (Kuhn, 1962) including subjective choices of system boundaries for analysis.

The fundament of agriculture is plant cultivation and accordingly the photosynthesis. This chemical reaction is a powerful phenomenon, or as Neil A. Campbell et al. (2018) put it: “No chemical process is more important than photosynthesis to the welfare of life on Earth” (p. 279). It should be kept in mind that plants conduct both photosynthesis and cell respiration (Figure 1).

FIGURE 1 The net effect of photosynthesis and cell respiration. Illustration: The author and Depositphotos

The net effect from these two chemical processes is a positive climate effect and the process behind it can be summarized like this: Huge amounts of CO₂ are caught every year by crops that, in turn, generate huge amounts of O₂, which is good for the climate. At the same time these crops bound C in their shoots and roots (1 in Figure 2) including rhizodeposition (Whipps & Lynch, 1985). Regarding organic C left in the fields as a result of roots alongside residues from shoots, estimations point at 2750 Tg annually on a global level (Paustian et al., 2016). Sometimes farmers remove straw at harvest and use it as a fossil-free energy source, or for animal care after which the straw returns to the fields as farmyard manure.

FIGURE 2 The two kinds of carbon-binding in crop fields: Soil organic carbon and carbohydrates exported directly or indirectly (via animal feed) to the industrial or consumer sector. Illustration: The author and Depositphotos

Parts of the shoots results in cereals, for example, 2719 Tg in 2019 estimated by FAO (2020). This means 2311 Tg dry matter containing 1040 Tg C, which is equivalent to 3825 Tg CO₂ (calculations based on data from Alias & Linden, 1991 and Linderholm, 2014). And this was just cereals like wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena sativa L.), and rye (Secale cereale L.). Other large crops are oil plants, potato (Solanum tuberosum L.), sugar beet (Beta vulgaris L.) etc. Agriculture thus binds huge amounts of CO₂ each year in the form of cereals and other crop products (2 in Figure 2).

However, this last-mentioned photosynthesis effect is not fully considered to be a positive contribution from the agricultural sector neither in many general discussions in society (Linderholm, 2012) nor in the IPCC calculations. Instead IPCC treats “harvest removal” as something lost, disturbing, negative, and equivalent to emissions. Consider this citation: “The default assumption is that all biomass lost is assumed to be emitted in the same year” (IPCC, 2006, p. 5.10). The IPCC defines C binding as something that occurs on the plant sites and they seem to only consider C that stays there as a positive thing. Compare this citation: “Net Biome Production denotes the net production of organic matter in a region containing a range of ecosystems (a biome) and includes, in addition to heterotrophic respiration, other processes leading to loss of living and dead organic matter (harvest, forest clearance, and fire, etc.)” (IPCC, 2000, p. 34).

The argument for not taking harvested products into account as a positive contribution might have been that bound C in food will generate CO₂ when consumers, at a later stage, process it through their digestion. But that emission is made primary by other sectors in society than the agricultural sector, and it occurs at later points in time. It has to be underlined that the consumer sector, for example, can be defined as being outside the system boundary of the agricultural sector. In light of this, one may find it strange that agriculture so often is accused for its negative climate effect, but does not at the same time get laudation for its positive C-binding and oxygen production.

The science community is aware of the positive effect from the photosynthesis in agriculture. Researchers have even tried to improve the photosynthesis. In 2012 the international research project Realizing Increased Photosynthetic Efficiency (RIPE) was started, funded by the Bill and Melinda Gates Foundation. The aim partly was to make crops more productive by improving the photosynthesis through DNA technology. One amazing result was published in 2016 about the inefficient use of light (Kromdijk et al., 2016). To avoid damage, plants turn the photosynthesis off when sunlight gets too strong. This light-quenching mode, however, is continuing a bit also after a cloud, for example, has moved in. The team at RIPE modified genes in plants so that they speeded up the return of the photosynthesis. As a result, the amount of biomass in these plants improved by about 15%.

The consequence of that IPCC not fully counts the harvested fraction of the photosynthesis result as a climate contribution, and therefore does not include the total positive climate effects of agriculture, might be that policy makers will act in a way that can affect agriculture production in undesirable ways. These actions can in turn be analyzed from a holistic sustainability point of view. For example, as I have described in The Lancet, reduced food production (if, for example, reduction becomes a result of political actions based on climate concern arguments) can lead to social and medical disasters (Frankelius, 2019). Moreover, positive factors that stimulate biodiversity, such as natural pasture lands, can be hampered if agriculture has less favorable conditions for developing.

The sustainability perspective applied here was fueled by Gro Harlem Brundtland (1987) and she regarded sustainability as a balance act including ecological, economic, and social dimensions (Brundtland, 1987). In September 2015, the United Nations adopted a still broader perspective through the 17 sustainability goals. Interestingly enough the first goal was formulated like this: “End poverty in all its forms everywhere” and the second: “End hunger, achieve food security and improved nutrition, and promote sustainable agriculture”. Both are related to economic aspects and food production needs. The 13th goal was about climate action: “Take urgent action to combat climate change and its impacts” (United Nations, 2015, p. 18). But despite 17 goals only one of them, climate action, was top of mind for many during 2019. The Economist editor Catherine Brahic put this into a critical perspective when concluding “Efforts to protect biodiversity have been overshadowed by the climate fight. Might 2020 be different?” (Brahic, 2019, p. 84).

Although agriculture is contributing positively to climate already through C-binding and oxygen production and diffusion, there is more to be done in terms of reducing the negative greenhouse gas emissions, as well as boosting the catching of CO₂. Let me pinpoint some pathways, besides the RIPE project:

Bare soil does not bind as much CO₂ as does soil covered by vegetation, but still we find bare soil in agricultural landscapes. There is a potential to make farming fields greener, but that is depending on proactive and skillful farmers that also have the economic ability to invest in new equipment and are willing to take the risk of innovation. One such farmer is Benoît Vernillat. He has the 500 ha farm SARL Travagri in France and is part of a competence network called GIEE Magellan including 40 farms. This network has its geographical base in the district of Nièvre in the Burgundy–Franche–Comté region. Together with advisors such as Michael Geloen at the organization Terres Inovia, Vernillat's network has succeeded in combinations of annual and perennial crops including main and cover crops. They also manage to sow new crops directly in growing crops. Terres Inovia experiments with perennial crops based on leguminous (like alfalfa [Medicago sativa L.], lotus [Lotus corniculatus L.], berseem clover [Trifolium alexandrinum L.], and white clover [T. repens L.]), and annual cover crops {like niger [Guizotia abyssinica (L. f.) Cass.], Abyssinian mustard [Brassica carinata A. Br.] and lacy phacélia [Phacelia tanacetifolia Benth.]}. Regarding alfalfa, most sources tell Carl Linnaeus (L.) as authority. However, it probably was the French botanist Joseph Pitton de Tournefort (T.) or the German physician Augustus Quirinus Rivinus (Rv.), according to the translation and analysis of the original writings of Linnaeus (Frankelius, 2007). Different crops stimulate different aspects (e.g., C storage, N₂ fixation, weed control, and soil structure stimulation) in different degrees. Among the challenges Vernillat faces are slugs, field voles, weeds, and fungal diseases but also restrictions on the use of chemical agents. New machinery is needed to succeed, and development is ongoing at many companies, not the least is seeder, planter, and row-hoeing producers.

Fertilizers – both mineral and organic – can improve the photosynthesis if the level at the starting point is below biological optimum (Thomas Keller, personal communication, 2020). The availability of manure depends on the equestrian sport as well as meat and milk-product consumption in society and one pathway therefore is marketing of the climate-related ecosystem services provided by e.g. livestock. Regarding mineral fertilizers innovation is ongoing around its production. The company Yara, for example, is currently building pilot plants to produce fossil-free mineral fertilizers. In 2023, the company probably will launch fossil-free fertilizers produced by means of water power in Norway and solar energy in Australia. In Sweden, production of fertilizers out of clams is on trial by Water Center East. In the same country the company Biototal takes care of the by-product ammonium sulfate out of the SSAB steel production and offers it for farm use.

Another promising concept is spreading more biochar on agricultural fields. Biochar is bound C in itself and also contributes to soil health that in turn improve harvest. Biochar can be produced by sustainable forestry and thus the combination of agriculture and forestry, therefore can contribute to the vision of climate improvement. The use of biochar is already substantial (not the least in North America) but has potential of expansion.

Moreover, there are possibilities to expand fossil-free agricultural machinery. Options for replacing diesel energy include fuel cells (like the NH₂ prototype from New Holland, Cursor X from Fiat Powertrain or the pioneer Allis Chalmers in 1959) as well as cable-borne electrical vehicles (like John Deere's Gridcon), but both concepts need to be powered by fossil-free energy if being climate-good. Other concepts are biogas engines, biodiesel engines, and even modern steam engines powered by, for example, straw pellets (like the Ranotor concept).

Another potential innovation is called agrosolary. Like agroforestry trees are planted in avenues over arable land. Then solar panels that follows the sun (trackers), having “organic design”, are placed in these tree avenues. Thus, the farmer can harvest not only crops from the fields but also sun energy directly, which can then be used for electrical tractors such as Fendt e100 Vario, HAV, or RigiTrac; or robots such as Robotti (Agrointelli), Oz (Naïo Technologies), or X-tractor (Kubota). The concept, that also improves biodiversity and decrease wind erosion, is developed by the farmer and inventor Kurt Hansson in Sweden, and is based partly on a new type of patented hydraulics (including an actuator) from an aircraft manufacturer.

Last but not least new technologies such as tire construction, automatic tire inflation systems, lightweight material, and small autonomous vehicles can decrease soil compaction. Easy-drawn implements like seeding or inter-row-hoeing machines with self-seeking coulters can also reduce soil compaction because they do not need heavy tractors. Lower compaction, in turn, increases yield and can reduce anaerobic reactions in the soil and therefore also reduce emissions of both CH₄ and N₂O (Ball, Scott, & Parker, 1999).

ACKNOWLEDGMENTS

I am grateful for the comments on earlier versions of this manuscript by anonymous reviewers. I am also grateful for research funding from Sweden's innovation agency Vinnova and Region Östergötland. The research and innovation program Agtech 2030 at Linköping University has been platform for parts of the research behind this article. Finally, I got valuable ideas from Magnus Börjeson (AgroÖst), Crister Stark (Väderstad), Magnus Åhman (Åhmans Traktorcentrum), Cilla Krantz (Agro Sörmland), Lars Askling (Gothia Redskap), and Mats Tykesson (Kverneland). But of course, I myself account for all possible errors and shortcomings in the article.

The author declares no conflict of interest.

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