Scenarios, Challenges and Opportunities for Sustainable Agricultural Chemistry

Author

Sílvio Vaz Jr. Chemist, D.Sc. in Analytical Chemistry, research scientist at Embrapa Agroenergia, Brasília, DF, Brazil; silvio.vaz@embrapa.br

Introduction

In the 20th century, more precisely, after the Second World War, the evolution of agriculture reached one of its most important hallmarks in what became known as the Green Revolution. This period was based on a set of agricultural practices and techniques based on the introduction of genetic improvements in plants and the evolution of agricultural production apparatuses to expand, above all, food production (Pingali, 2012). Although the Green Revolution is heavily criticized for its environmental impacts and the process of land concentration that accompanied its evolution due to policies that were used to promote the rapid intensification of agricultural systems and increase food supplies (Pingali, 2012), its importance for the development of agriculture in the world is undeniable. Furthermore, improvements resulting from novel technologies in the following decades, such as biotechnology, are still increasing agricultural productivity. Table 1 describes the main crops cultivated worldwide and their production. These values would not be achieved without the use of agrochemicals, brought to the scene by the Green Revolution.

Currently, agriculture must constantly become increasingly more sustainable, with the reduction in its negative impacts on the environment being matched with the demand to increase its positive impacts on society and the economy.

These are challenges and, at same time, opportunities for new production systems.

The United Nations (2019) established 17 sustainable development goals to promote sustainable global growth. Goal 2 (zero hunger) is closely related to agriculture and food security; according to this goal, “a profound change in the global food and agriculture system is needed if we are to nourish the 815 million people who are hungry today and the additional 2 billion people expected to be undernourished by 2050.” Thus, agriculture has a paramount responsibility to find ways to provide food for such increasing demand in the years ahead. At the same time, devising ways to reduce impacts associated with agricultural production that could be considered harmful to the environment is also key.

Chemistry and Agriculture: A Direct Relationship

The contribution of chemistry to agriculture goes back to the 19th century, with the synthesis of inorganic fertilizers and of, by the middle of the last century, a large number of compounds synthesized to control insects, diseases and weeds (Pinto-Zevallos; Zarbin, 2013). 

This contribution is clearly and decisively observed in the cycle of nitrogen, an essential element to most molecules that integrate organic matter. Plants, with some exceptions, do not have the capacity to absorb this element from the atmosphere (with 78% nitrogen), the opposite of what occurs with another essential element, carbon, which is absorbed as CO2 via photosynthesis. The only natural way to close the nitrogen cycle is through the decomposition of organic material from dead animals or plants or through excretion from living things; this form of replenishment is naturally limited (Killops; Killops, 2013). Another natural method, the biological fixation of nitrogen from the atmosphere by some microorganisms and its later release as part of organic matter, although of utmost importance to maintain life on the earth, does not suffice to add nitrogen to meet the high demand presented by modern agriculture.

The capture and use of atmospheric nitrogen in the soil has only been economically possible via the works of the German chemists Fritz Haber and Carl Bosch. They developed the Haber-Bosch reaction or process at the beginning of the 20th century (Ritter, 2008), a reaction that allows the synthesis of ammonia from low-reactivity atmospheric nitrogen and another abundant element, hydrogen, on the industrial scale. Curiously, the incentive that led to this essential innovation was not initially the production of fertilizers but the production of nitrates for military purposes (explosives) to be used in World War I.

Ammonia, a molecule with approximately 82% nitrogen by weight, can be absorbed by plants through the soil after intermediation by microbiological processes that produce ammonium and nitrate. Due to the ease of application, the use of solid substances derived from ammonia, such as urea and ammonium nitrate, as a nitrogenous fertilizer is preferred. The world production of ammonia today reaches approximately 140 million tons per year (United States Geological Survey, 2017), and almost all global production is intended for the synthesis of industrial fertilizers. The percentage of the world population whose food depends on the use of synthetic nitrogen fertilizers is estimated at 53% (Liu et al., 2016). 

Taking nitrogen fertilizers as an example, we can conclude that so-called organic farming, which advocates for the exclusion of synthetic fertilizers, can function as a niche market in societies of abundance, but it is certainly not an alternative to feed the entire human population. This example clearly shows the contribution of agricultural chemistry to the well-being of modern society.

Agrochemicals and their Usages 

According to Stephenson et al. (2006, p. 2082), an agrochemical is an “agricultural chemical used in crop and food production, including pesticide, feed additive, chemical fertilizer, veterinary drug, and related compounds”. Currently, we can observe several agrochemical classes according to their uses in agriculture (International Union of Pure and Applied Chemistry, 2019)

• Fertilizers - any kind of substance applied to soil or plant tissues to provide one or more nutrients essential to plant growth;

• Plant growth regulators - (also called plant hormones) - several chemical substances that profoundly influence the growth and differentiation of plant cells, tissues and organs; and

• Phytosanitary products, pesticides or correctives: herbicides, insecticides, fungicides, acaricides, bactericides, rodenticides, nematicides, repellents, fumigants, disinfectants, antibiotics, defoliants, and algaecides (or algicide). Agrochemicals move a huge global market that is expected to reach 250.5 billion USD by 2020 (Statista, 2018). However, agrochemicals are one of the main classes of chemical pollutants, with serious negative impacts on public health and the environment (Public…, 1990; Nicopopoulou-Stamati et al., 2016). The search for alternatives to conventional agrochemicals presents itself as an excellent opportunity for the development of sustainable agricultural technologies and for opening new businesses. 

Impacts of Agriculture on the Environment and Health

Governments, farmers and consumers show increasing concern related to the negative impacts of the large amount of inputs applied to produce different crops in different regions around the world on the environment and health. Agrochemicals are directly correlated to damage from agriculture, with pesticides with toxicological implications being the main representative class. In general, the main negative impacts of agriculture on the environment are:

• Water, soil and air pollution due to pesticide applications;

• Depletion of water bodies due to high water demand;

• Erosion and soil degradation due to inadequate management during cultivation;

• Change in biota due to factors already listed;

• Changes in the quality of environmental resources also due to factors already listed;

• Ecological risks for insects, plants and animals associated with the change of the environment; and

• Climate change due to deforestation and biomass combustion.  

Regarding the impacts on health, the following can be highlighted:

• Poisoning due to pesticide use and contaminated food consumption;

• Occupational risks to farmers due to the exposure to pesticides; and

• Human infections or emerging infectious diseases that do not respond to treatment due to the use of antimicrobials in agriculture (Grace, 2019).

From these negative impacts, the development of more environmentally conscious and health-friendly agriculture is becoming paramount.

Sustainability and Agricultural Chemistry  

Agricultural chemistry is, undoubtedly, one of the fields of research and business whose impact is felt throughout the world, since we all need to eat to survive. Added to this is the fact that, increasingly, technology is intertwining with modern agriculture both regarding new production strategies and the reduction of negative environmental impacts (Herman, 2015). Sustainability can be seen and understood by means of its three components: environmental impacts, economic impacts, and societal impacts. Impacts can be positive or negative according to their direct or indirect effects upon the environment, economy and society. Considering that agrochemistry is the application of chemistry and its concepts and technologies to promote better agriculture, economic and societal impacts are expected to be positive, especially the economic impacts. On the other hand, and due to a history of incidents at the global level, environmental impacts are expected to be negative; nevertheless, they could be positive if modern technologies and good agricultural practices are used. A more detailed evaluation of sustainability in agriculture can be seen in Quintero-Angel and González-Acevedo (2018).  Sustainable chemistry, a recent branch of chemistry, was defined as “(…) a scientific concept that seeks to improve the efficiency with which natural resources are used to meet human needs for chemical products and services. Sustainable chemistry encompasses the design, manufacture and use of efficient, effective, safe and more environmentally benign chemical products and processes.” (Organization for Economic Co-operation and Development, 2019a). From these statements, a relationship with agricultural chemistry can be constructed by means of the design, manufacture and use of efficient, effective, safe and more environmentally benign agrochemicals. That is, it can be achieved by the establishment of a strong innovation drive in agriculture for the next decades. Furthermore, goals 9 and 12 for the sustainable development depict the necessity of industry, innovation and infrastructure allied to responsible production and consumption (The United Nations, 2019).  

New Technologies and Trends 

Some areas of recent technological development closely related to agricultural chemistry have a direct impact on agriculture, and their usages represent trends to be considered in both the short and long term.  Figure 1 depicts the relationship between agricultural chemistry and related scientific and technological fields as an interdisciplinary theme.

Analytical & environmental chemistry can provide technological chemistry input techniques, technologies and knowledge that could be essential to analyze, produce and monitor more efficient agrochemicals. Nanotechnology and biotechnology are new technological approaches that can be incorporated to improve agrochemicals aiming for better agronomic performance. Food security and the environment are closely related to agrochemical use and near to the consumer, involving laws, market restrictions and public opinion. Finally, sustainability is a strong demand by society for better quality of life and greater transparency in the productive chain.

Figure 1. Relationship between agricultural chemistry and related areas of study and technological development. 

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Vaz Jr., Sílvio. Scenarios, challenges and opportunities for sustainable agricultural chemistry / Sílvio Vaz Jr. – Brasília, DF : Embrapa, 2019. PDF (35 p.) – (Documentos / Embrapa Agroenergia, ISSN 2177-4439, 30) 1. Agrochemicals. 2. Biotechnology. 3. Sustainability. I. Serie. CDD (21. ed.) 630.2745