Reducing GHG emissions
The primary sources of greenhouse gas emissions associated with agriculture include:
- Enteric fermentation (ruminant digestion)
- Manure management
- Agricultural soils (soil disturbance and fertilizers)
- Deforestation on agricultural land
There are three greenhouse gases relevant to primary agricultural activities: Carbon dioxide, methane and nitrous oxide. Methane has approximately 23 times the greenhouse gas impact of carbon dioxide and is released primarily through livestock digestion and manure. Nitrous oxide has about 310 times the greenhouse effect of carbon dioxide and its main agricultural sources are soil disturbance and fertilizer application. Carbon dioxide itself is primarily released through the burning of fossil fuels for energy and the operation of farm equipment.
Measuring the specific emissions associated with agriculture is complex because of the range of agricultural practices, inputs and technology and the variables of soil, climate and land cover for each farm. Nonetheless, there are clear opportunities for emission reductions in agriculture and many are associated with long-term cost savings.
Certain farm practices are commonly identified as reducing agricultural greenhouse gas emissions.
- Cropland management
- Livestock management
- Energy efficiency and renewable energy technologies
Croplands are frequently managed intensively and provide a number of opportunities to reduce net greenhouse gas emissions (and sequester carbon) through adjustments to farm practices. Some cropland management practices may simultaneously reduce emissions and provide increased carbon sequestration (emission removal).
Improvements in agronomic practices (that often also improve yields) can increase soil organic matter and reduce erosion which also increases soil carbon levels. Practices that utilize excess nitrogen (such as cover cropping) can also reduce nitrous oxide emissions. Some examples of these practices include:
- Using crop rotation systems
- Decreasing summer and bare fallow
- Using cover crops following harvest (particularly through the winter)
Improving the timing and rate of nitrogen fertilizer application can help to prevent leaching/runoff and emissions of nitrous oxide (N2O) that result from surplus nitrogen. Efficiency of uptake also reduces the amount required, resulting in cost savings for the producer.
Nutrient management practices linked to GHG emission reduction include:
- Reducing the use of excess fertilizer, pesticide and other inputs
- Adjusting fertilizer applications to suit the precise needs of the crop
- Timing applications to minimize fertilizer loss (through runoff etc.)
Improved feeding practices
More research is needed on feeding practices that decrease methane released through enteric fermentation. However, some practices believed to reduce quantities of methane are:
- Improving pasture quality and extending the grazing season
- Using high quality feeds including careful selection of forages (for example inclusion of legumes in forage mixes has been shown to reduce energy lost as enteric methane)
- Adding fats or oils to ruminant diets (small quantities of plant-derived oils such as canola and soybeans are linked to increased energy density and decreased methane emissions)
Animal manure can release substantial amounts of the greenhouse gases nitrous oxide and methane. The gases released by manure can be mitigated through management practices such as:
- Covering manure storage
- Improving efficiency of manure as a nutrient source – improving timing and rate of application
- Collecting and combusting methane
Reducing energy consumption has the potential to offer “win-win” solutions for farm business by reducing operating costs at the same time as carbon footprints. Opportunities to improve energy efficiency depend on the technologies and energy conservation practices currently utilized as well as the available alternatives. For detailed information regarding agriculture and energy efficiency please see Saving energy on your farm.
Renewable energy technologies
Opportunities for generating clean energy on-farm will depend on the type and scale of operation and its location.