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Use of agricultural resources and residues puts environmental balance in deficit

11 December 2020

Researcher does material flow accounting and warns of high consumption of non-renewable resources that cause damage, such as nitrogen and phosphorus, writes Valéria Dias in the Journal of USP

In the last 20 years, Brazil has had a great productivity gain in agriculture and livestock, producing more with less nitrogen, phosphorus and potassium - macronutrients used as fertilizer and indispensable for plant and, consequently, animal production. But according to research by USP's Faculty of Veterinary Medicine and Zootechnics (FMVZ), both the absolute consumption of these nutrients and the generation of waste increased considerably, producing a great environmental impact.

“There is a large consumption of finite natural resources and the generation of waste without any concern with the cycling of these resources. In the future, this may become unsustainable ”, warns Professor Augusto Hauber Gameiro, from the Department of Nutrition and Animal Production at FMVZ, in Pirassununga.

The data are in Gameiro's postdoctoral research, carried out at the AgroParisTech University , in France. The work provides an estimate of the consumption of nitrogen, phosphorus and potassium involved in the five main systems of animal production in Brazil: beef cattle, dairy cattle, laying poultry, beef poultry and swine, between the years 1992 to 2013. An article on the subject, Nitrogen, phosphorus and potassium accounts in the Brazilian livestock agro-industrial system , was published in the Regional Environmental Change magazine .

To reach the results, the professor relied on material flow accounting and industrial metabolism. The first is the sum of everything that enters and everything that leaves a system (in this case, the production and consumption of nitrogen, phosphorus and potassium from the five animal production systems, between 1992 and 2013). The concept of industrial metabolism, on the other hand, is inspired by the functioning of a cell, but it extrapolates to a larger scale, which can be a given system, a city or even a country. The data were obtained from sources such as the Brazilian Institute of Geography and Statistics (IBGE) and other public information banks, in addition to literature and interviews with specialists in the sector.

The results point to the need to better reuse non-renewable resources, such as phosphorus and potassium, and to reduce the use of those that cause damage to the environment, such as nitrogen and phosphorus. These two elements, recalls the professor, are recognized as major causes of environmental problems. As for potassium, Brazil has no natural reserves and needs to import it. Another problem is that the country is highly dependent on these fertilizers.

Gameiro also suggests the adoption of crop-livestock integration, a technique also known as rotation of annual crops with pastures, in which producers use the land for animal and vegetable production, performing a rotation between them, according to the time of year.

In Paris, the fertilizer is in the sewer

The professor also cites as an alternative the use of human and animal waste as fertilizers. “ In Paris, [the capital of France] all the city's sewage is treated, transformed into fertilizer and used in local agriculture”, he exemplifies. For him, without nutrient cycling there is no sustainability. “To be sustainable, there must be a social, environmental and economic tripod. If there is only the economic factor, it is not sustainable ”, he says. He recalls that the 3R concept (Reduce, Reuse, Recycle) is already known in the industry and used in the tire sector, pesticide packaging and computer equipment, among others.

Gameiro says that when he arrived in France, he had a reality check when he realized how Brazil is totally behind in terms of research on sustainability in the agricultural sector. According to him, in Europe, agricultural science, animal production and zootechnics developed there take the environmental issue very much into account.

Challenges

The professor ponders that, today, bringing sustainability to the sector is still difficult, however, viable. He talks about the southern states of Brazil, where it is common to find rural properties that use crop-livestock integration in their properties and use animal waste as fertilizer in the various crops they plant.

In large monocultures such as soy, cane and corn, so common in the Brazilian Midwest, this becomes something much more complex. “There are many agronomic, logistical and environmental challenges”, he points out.

Planetary boundaries

The unlimited use of phosphorus and nitrogen faces yet another problem. Articles published in 2009 in Nature and in 2015 in Science cite the Planetary Boundaries , nine safe environmental limits that humanity must not exceed, at the risk of causing serious and even irreversible damage to the planet. They are: climate change; loss of biosphere integrity and species extinction; change in land use; the biogeochemical cycles of phosphorus and nitrogen; degradation of the ozone layer; ocean acidification; global use of fresh water; concentration of atmospheric aerosols; and chemical pollution.

The idea was proposed in the article A safe operating space for humanity published in Nature , in September 2009, by a group of 29 researchers worldwide, including Johan Rockström, from the University of Stockholm, Sweden. In 2015, the group published a new article, this time in Science , Planetary boundaries: Guiding human development on a changing planet , where they point out that the first four borders mentioned above have already been crossed. The phosphorus / nitrogen cycle is one of them.

 Montage with photos by: Marcos Santos / USP Imagens and Marcelo Camargo / Agência Brazil

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