Greenhouse gases, the impact of agriculture
The greenhouse effect is a natural phenomenon that has the effect of retaining solar heat in the atmosphere. However, negative effects are revealed with the constant increase of human activities (industries, agriculture, various human activities). When we talk about GHGs (greenhouse gases) we refer to three main gases:
– Carbon dioxide (C02)
– Methane (CH4)
– Nitrous oxide (N20).
Water vapour and tropospheric ozone should also be mentioned.
Since 1997, when the Kyoto Protocol was signed, numerous measures have been put in place by governments to curb and reduce GHG emissions from human activities. However, a recent UN report mentioned a 2% increase in global GHG emissions in 2019.
The IPCC (Intergovernmental Panel on Climate Change), a United Nations agency, identifies five main sources of GHG emissions
– Energy (electricity and heat production from fossil fuel power plants): 35%.
– Agriculture (soil mineralization, methane production from rice cultivation and enteric fermentation of livestock) and forestry (deforestation, forest fires and crop burning): 24%.
– Industry (heavy industry and manufacturing): 21%.
– Transportation (goods, people): 14 %
– Building (construction, maintenance, electrical and heating of residential and non-residential buildings): 6%.
Agriculture thus represents a significant share of GHG emissions, almost 25%.
GHGs and agriculture
The percentage of GHGs attributable to agricultural activities varies according to the practices and measures put in place by countries wishing to reduce their emissions. China and India are the largest agricultural GHG emitters (source: FAO).
Between 1990 and 2017, total GHG emissions from Canadian agriculture increased by 26%, according to Statistics Canada. The Canadian average for all sectors combined was +19%.
Despite this increase, only 10% of Canada’s GHG emissions originate from agriculture (excluding emissions from fossil fuel consumption and fertilizer production).
In Quebec, in 2017, the agriculture sector emitted 9.8% of GHG emissions into the atmosphere, or 7.7 Mt CO2eq.
In the agricultural sector, GHG emissions come from animal digestion, enteric fermentation (especially cattle), manure/slurry management and agricultural soil management.
In Quebec, in 2017, enteric fermentation, agricultural soil management and manure management produced the largest share of these emissions, respectively:
Enteric fermentation :37.3%,
Agricultural soil management: 31.0% and
Manure/slurry management: 26.6% of the sector’s total.
Enteric fermentation is a digestive process. Microorganisms in the stomach and rumen break down food to allow its absorption into the animal’s bloodstream. This fermentation process results in the formation of methane gas. Methane has a calorific value 28 times more powerful than CO2. In agriculture, it is emitted by enteric fermentation, animal feces and rice cultivation. Worldwide, it is estimated that about 2 billion tons of CO2 eq. are emitted from enteric fermentation of livestock.
Conventional management of manure and slurry generates CH4 and N20 emissions, whereas agricultural practices (crops) are more concerned with CO2 and N20 emissions, notably using chemical fertilizers.
GHGs and pig farming
The carbon balance for a product consists of an estimate of the GHG emissions during all the stages related to the production of the product, from the extraction of raw materials to the finalization of the product.
Thus, the carbon balance of hog farming in Quebec considers all the steps involved in the production of pork meat, specifically from the production of grain for the feed to slaughter. The 2016 results show a carbon balance of 4.22 kg CO2e/kg pork carcass. The world average is 6.12 kg CO2e/kg. These 4.22 kg CO2 eq/ per kg pork carcass are distributed according to the following items:
Grain production for feed (complete agricultural process, including use of pesticides and fertilizers): 2.35 kg CO2 eq.
Pig breeding: 1.55 kg CO2 eq.
Slaughter: 0.32 kg CO2 eq.
Greenhouse gas emissions produced by hog operations come from three main sources.
– Enteric digestion of animals. Animal feed plays an important role in GHG emissions, as does the production of grain for feed and the use of chemical fertilizers for their cultivation.
– The manure pit (anaerobic digestion)
– Spreading manure
In addition to this, there are secondary sources that can be summarized as follows:
– Fossil fuels used to heat buildings and/or generate electricity on the farm,
– Fossil fuels used to transport and spread manure,
– Fossil fuels used for agricultural machinery.
How to reduce GHG emissions in pig farming
The storage of manure in pits is a major source of methane emissions.
In this anaerobic environment the volatile solids, undigested components of the feed, are transformed into methane by bacteria. To limit fermentation, the solution tracks are :
– Adapt the diet of the animals to reduce the presence of these volatile solids.
– More frequent spreading as much as possible.
– Install a cover on the pit with a gas recuperator. However, the costs are significant and there is a risk of hydrogen sulphide build-up under the cover.
Nitrous oxide is emitted during spreading. Incorporating the slurry into the soil as soon as possible will limit the release of volatile nitrous compounds.
In the hog barn, the type of floor, the cleaning technique and its frequency are all factors that can influence GHG emissions.
The Solugen contribution
Solugen’s solution offers multiple advantages both economically and environmentally.
By treating the slurry directly from the pre-pit, it no longer needs to be stored in a pit. Furthermore, during the process, the manure is divided into a solid fraction which represents approximately 10% of the initial volume of manure, and a liquid fraction which after treatment will be divided into pure water, concentrated potassium bioliquid and an ammonia solution.
It is therefore estimated that 90 to 95% of the GHGs normally emitted during manure storage and spreading are eliminated. For a farm that produces 10,000 m3 of manure annually, this reduction represents some 572 t Co2 eq.