When we talk about climate and environmental sustainability, we also hear about “Carbon Footprint“. But what is the meaning of the “Carbon Footprint” of food, and how is it calculated?
All human and natural activities cause the emission of greenhouse gases into the atmosphere, such as carbon dioxide and methane. These can be created by using fossil fuels, production and consumption of food, industrial activities, transport and other services. The total greenhouse gas emissions are the “Carbon Footprint”, expressed as equivalent carbon dioxide. The carbon footprint is one of the most widely used indicators to describe the level of sustainability of a product or activity to assess its impact on climate change.
To calculate the Carbon Footprint to minimize evaluation errors, you need to consider the entire life cycle of a product or activity you are analyzing. In this way, it is possible to identify critical issues at specific points in a production chain and maximize their efficiency to reduce their impact. In particular, it appears that fossil fuels are still the primary source of emissions.
Despite the rumours and fake news, the agricultural sector has the lowest greenhouse gas emissions, estimated at 12% of the total, concerning the increase in population. This shows that the technological innovations in agriculture allow the production of an increasing amount of food with limited impacts. The latest FAO data also confirm the virtuousness of the agricultural sector. They show a significant reduction in emissions, thanks to increased efficiency in agriculture and livestock supply chains.
But which gases contribute to the greenhouse effect? The most relevant are carbon dioxide (CO2) generated by the use of fossil fuels, methane (CH4) of enteric fermentation of cattle digestion and their slurry management, and nitrous oxide (N2O) due to the use of natural or synthetic nitrogen fertilizers. These three substances contribute differently to climate change because of their different chemical-physical behaviour. Emitting one gram of methane is like emitting almost 30 grams of CO2, while one gram of N2O corresponds to 265 grams of CO2.
Nitrous oxide is one of the most critical gases because its unit impact is high even if the quantities are low. The protoxide is created by the bacteria in the soil during the assimilation of fertilizer by plants. However, it is much more complex than it seems. When calculating the greenhouse gas emissions of an agri-food system, we must also consider the “biogenic emissions“, which are not polluting because they return into a natural cycle.
While in the case of fossil fuels, new polluting CO2 is generated, which will return coal only in millions of years. In the case of agricultural production, the growth of biomass as plants or animals allows absorbing part of the CO2 emitted. This lets to look at the problem from a new perspective. Indeed, although agricultural and livestock systems are a source of greenhouse gases, it is also true that processes can absorb some of the emissions thanks to a natural cyclic flow, regulated by a continuous exchange between plants, animals and the surrounding environment.
This aspect, never considered before, opens new opportunities for agricultural and livestock operators. For example, they are enhancing practices that allow generating “carbon credits” to be used as compensation in their value chain. To evaluate agricultural systems as “zero impact“, the emission-absorption cycle must be balanced, with a time lag as short as possible between the moment of emission into the atmosphere and the complete absorption of that CO2. The problem with fossil fuels is that they regenerate in millions of years, therefore with too long compared to those emitted into the atmosphere.
In short, the different permanence of gases in the atmosphere must be taken into account. The greenhouse effect is calculated over 100 years, although the various substances have very different behaviour. Once carbon dioxide is emitted, it can persist in the atmosphere and affect the climate for over a thousand years. On the other hand, even if it has a greater impact, methane has a much shorter permanence time of about ten years. In the calculation of the Carbon Footprint, it would be necessary to separate the emissions derived from fossil fuels from the biogenic ones, which arise from biological systems.
All these considerations make it possible to say that agriculture and animal husbandry if managed in the right way, can be a solution to climate change rather than a problem.
