A Matter of Methane

Thursday, June 23, 2022

Possible solutions to lessen methane and other greenhouse gases produced by the agricultural sector

By Kristen Lutz

Methane is back in the hot seat, and agriculture is reminded that it's a contributor to global climate change. Farmers are very familiar with greenhouse gases (GHG) and their effects on the environment, so what makes this go-around different? New rules have been put in place, allowing farmers to better explore sources of renewable energy. Better Farming spoke to experts in agriculture sustainability to better understand this pressing issue.

Why methane?

Methane isn't the only GHG produced by agricultural endeavours; there's also carbon dioxide (CO2) and nitrous oxide (N2O). What makes methane the forefront of conversation? Perhaps because of "its presence in livestock systems in both terms of manure and magnitude; often rumen fermentation produces a lot of methane," says Christoph Wand, livestock sustainability specialist at Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). "In Ontario, we have other sectors that are bigger than ag: building, transportation, etc.," he says when discussing GHG emissions. "Within livestock, it's definitely methane that's the number one GHG we see."

Each sector of ag contributes in different aspects to overall GHG emissions. Ruminants, such as cows, goats and sheep, are a direct source of methane produced by fermentation in their gastrointestinal tract. But N2O is largely produced during crop production. "N2O from nitrogen fertilizer is certainly an important factor in feed production," says Wand. He mentions a study done by Egg Farmers of Alberta that looked at the GHG footprint of egg farmers determined "two-thirds of their production of GHG is surrounded by everything to do with feed production. So, some of these questions around tillage and nitrogen become very important," he adds.

Wand also says that we don't want to get too hung up on methane alone. "If we have CO2 coming from fossil sources – very old carbon. It will stay in the atmosphere much longer than methane. Long term, it has to be a balance between fossil CO2, methane and N2O combined."

The climate action plan

Drastic plans to reduce GHG emissions are becoming a worldwide imperative. This discussion has led to country leaders setting rules and limits to the level of GHG agriculture sectors can produce. Leaders from Ireland, New Zealand, and the U.S. are asking farmers to reduce GHG emissions by limiting cattle herd sizes and requesting additional trees be planted in ag landscapes. Although on paper these may seem like good ideas, they may not be the simple, most suitable solutions.

The connection between arboriculture and agriculture isn't new. The Trillion Tree Campaign of 2018 and the previous Billion Tree Campaign of 2006 followed similar practices of planting billions or trillions of trees worldwide to help combat climate change. "There's no doubt that trees have a role in this," says Wand.

"People overplay our photosynthetic role and our carbon fixing role as the same thing as carbon sequestration, which they aren't. Yes, we fix carbon. Yes, we photosynthesize carbon. But, if we're doing our jobs as farmers we're making effective use of that carbon and in the way of starch in feed reuse-it," Wand explains when talking about reducing agriculture's impacts on climate change.

Although carbon sequestration, which is ultimately the global goal, is in part done by photosynthesis, there are other tasks farmers can do to complete this cycle. "Some of these long-term no-till systems and some of the long-term grasslands with deep-rooted systems do it," Wand says when talking about carbon sequestration.

"Absolutely there's a place for trees in agriculture. People are really interested in silvopasture systems where we can add trees to uptake carbon and provide shade and mitigate erosion and so on, while still integrating beef and other grazing animals on pasture," he explains.

"You can't knock trees, there's no reason to. Has the usage of trees been oversold in these plans? Possibly. They're not effective unless there are other steps to the plan that are also being carried out. It's just one of several things."

Future, sustainable ag

Plans like these may be steps in the right direction to reducing our impacts on climate change, but they're truly just not enough. Innovation will be a key driver in creating more sustainable agriculture and reducing ag-related GHG emissions. "We talk all about efficiency in the agriculture world. I think part of the problem is that we start to confuse efficiency with actual sustainability," says Wand.

"We're farming more land with less fuel, but a large part of that is because we're farming with bigger equipment. At some point, we need to ask ourselves, at what point in time can we farm that same amount of land with no fuel? Those become really important questions and we don't know the answer."

Innovation is alive and well in economies such as electric cars or the use of sustainable material, which is helping to reduce our carbon footprint. However, agriculture doesn't seem to have quite the same level of transformation into less carbon-hungry alternatives. Although automated tractors and other technology are being introduced, they still have relatively large carbon footprints when we consider their building materials and fuel.

Finding ways to eliminate emissions and use a renewable energy source would be the most effective way at reducing the carbon footprint coming from agriculture. Wand concludes "the solution to this isn't ever bigger, it's more efficient equipment."

Carbon-negative biomethane

One of the solutions offered to producers is carbon-negative biomethane. This would consist of an anaerobic, meaning without oxygen, digester on-farm. Farmers could use this digester to trap methane and use that methane as a renewable energy source. Wand thinks this idea is "absolutely rock solid! These systems work exactly like everything we've learned about cows. Everything we do to reduce methane in ruminants is the exact same with these biodigesters, but opposite."

These systems could be slightly difficult to implement on farms depending on the production system. The initial cost is a big one, but the possibilities of these digesters are something that can help largely reduce agriculture's carbon footprint.

Jake DeBruyn, engineer for new technology integration at OMAFRA, agrees that digesters are a feasible solution. "Recently, we put in new rules under the Nutrient Management Act that allow farms to receive biodegradable waste to help boost the biogas production in anaerobic digesters; this is a permit-by-rule process. So instead of farmers saying, 'Well I might do this, I might do that,' under the Nutrient Management Act we say if you want to build an anaerobic digestor on your farm and you do these specific things, then you can have your system approved," DeBruyn explains. "These rules have existed since 2007, but in order to promote renewable natural gas, we recently made changes to these rules to make it easier for farmers to receive more and different feedstocks."

Currently, renewable natural gas production is only practical on a large scale, and the digesters that are found on farms are on a medium scale. But having something on a small scale, on a farm-by-farm basis, would be something any producer could implement and create self-sufficient, renewable energy.

"The ability to harvest your own biogas and apply it back to your farm can reduce electricity costs," says DeBruyn. But simple solutions are still in development. "If you have a manure pit, through the winter it's just too cold and simply adding a dome or roof wouldn't really be appropriate. If you wanted to create a digester that could harvest energy all year round, it would have to be an insulated tank with mixers and about 30 to 40 days of retention time – the amount of time the material would stay in the digester. It would have a rubber bubble on top and there would be some sort of co-generation system, generating electricity and heat, associated with it."

To make this sort of digester practical and economical, we would have to use each source of energy and products it provides back onto the farm. "The farm needs to be able to replace their energy use (net metering process) and the co-generation engines have a lot of heat that they blow off. We could use this heat to heat the milking centre wash water or to heat the barn or the house or the workshop. You could replace wood shavings or bedding material with digestate, the fibrous material from the digester," DeBruyn explains. "But for small-scale systems to work, you need to tap into several of these economical opportunities."

On a large-scale basis, anaerobic digesters would be taking organic material turning it into renewable natural gas and adding it to the natural gas grid. Ontario has the largest number of biodigesters in Canada with some farmers having long-term contracts with natural gas companies. These are companies who are looking for a renewable natural gas source to reduce their carbon footprint as well as farmers who are looking to gain a new source of profit.

Possibilities of biomethane

The primary motivation behind building these biodigesters is the ability to generate a new source of income while participating in the green energy economy, explains DeBruyn. "Whenever you produce natural gas and whoever purchases it doesn't need to purchase a fossil fuel natural gas. So, there's less fossil fuel natural gas and a reduction of GHG emissions.

"Farmers in the agri-food community have an opportunity to participate financially in the circular economy and the green economy. By doing this, ag is shifting and evolving, and this is just part of that evolution; part of that management tactic is capturing additional value," he says.

Other benefits make biodigesters appealing to producers. "When materials like manure, food waste and other ag or food processing by-products are put through the digester, there's a destruction of pathogens such as E. coli and Salmonella. So, whatever comes out of the digester has fewer pathogens in it," explains DeBruyn.

Implementing something like a biodigester can open doors for farmers to create partnerships with natural gas companies, and it may no longer be just the farmer investing their own money into their projects. "Because of the scale of these renewable natural gas projects, there will be new types of partnerships where farmers work with investors to build renewable gas systems. In this case, the farmer would be more of a sophisticated partner, and we may see new and different investment models," DeBruyn explains.

Essentially, the possibilities for this type of infrastructure on farms are endless. "Dairy is the perfect cookie-cutter (industry for) these systems," says Wand, and explains this is because of the already existing liquid manure pit. There's always room for growth in other sectors of ag. In "cash crop where there is a large volume of corn stover, and corn stover seems to continue to look like a great opportunity for these biodigesters," DeBruyn says. No aspect of these systems goes to waste. "The digester only harvests the portion of the organic material that's readily digestible; the other fibrous material is too resistant to biologically break down. The material that's not readily digestible will be applied back to the fields and it will stick around as organic matter. It returns back into the environment," explains DeBruyn.

Although the possibility of having an anaerobic digester on every farm may seem a bit futuristic right now, the science and evidence that these systems are possible solutions to global climate warming are there. With more of these digesters being put into place, the drive for each farmer to have their own is not far away. It appears to be a feasible, long-term solution to reduce GHG emissions associated with agriculture. BF