Slashing manure management challenges. Fighting energy costs. Dramatically boosting industry competitiveness in a new age of environmental pressures and expectations.
These are just a few of the reasons agriculture continues to play a strong role in both investigating and driving the rising opportunity for biogas production.
Biogas production is an option that is greener than any other gas technology and a good fit for a biobased industry that generates large volumes of organic byproduct, such as manure, feed spills, meat processing wastes and crop residues.
But just how practical and realistic is the biogas opportunity for agriculture? “There are a number of important questions and challenges,” says Mahendran Navaratnasamy, a research engineer with Alberta Agriculture and Rural Development. “But there’s no doubt the opportunity is growing. Biogas has the potential to be a very good fit for agriculture.”
The main drivers of the biogas opportunity for agriculture are the twin benefits of byproduct management –particularly livestock manure –and renewable energy production, says Navaratnasamy, the province’s lead technical advisor on biogas production. Both benefits are increasingly important against the current backdrop of environmental scrutiny and concern over fluctuating energy costs.
Technology advances, improved strategies and new ‘green’ regulations and funding incentives from government are making biogas production more feasible, he says. This is increasing the potential for biogas production to improve byproduct management, reduce on-farm energy costs and, particularly at a larger scale, create additional income opportunities.
“With the combination of pressures and incentives we see today, more producers are asking questions about biogas, and a growing number every year have taken the step of completing feasibility studies,” says Navaratnasamy.
Large scale biogas production systems for agriculture are not yet common, but there are several in North America, many more in Europe and this trend is expected to greatly increase worldwide over the next several years.
In Alberta, one major large scale biogas production facility has been implemented near Vegreville, Alta., designed as part of a Integrated Manure Utilization System (IMUS) originally developed and implemented through a collaborative effort between the Alberta Research Council and an industry partner, and supported by several additional government and industry stakeholder groups initially as a demonstration project.
The IMUS system at Vegreville is integrated with a large feedlot, has operated for two years, and currently has a daily production of about 20 tonnes of biofertilizer along with up to 24,000 kWh of green electricity from biogas that is directed into the Alberta power grid.
Other large scale systems are under consideration, and at least five smaller scale systems are being used by agricultural operations in Alberta.
In 2007, the Alberta Energy and Utilities Board (EUB) announced the approval of plans for the development of a 3.2 megawatt biogasfuelled power plant on the eastern edge of Lethbridge.
Various players are also exploring the opportunities for integrating biogas production with the production of other alternative fuels such as ethanol and biodiesel. At least two integrated production plants are under development in North America –one in Nebraska and one in Ontario.
WHERE BIOGAS FITS
The main question producers have about biogas production is whether or not this option is practical and feasible for their operation, says Navaratsamy.
The answer depends greatly on the size of the operation and / or the business opportunity envisioned, since there is a big difference in requirements, logistics and economics between small scale and large scale systems.
Understanding these differences and considerations starts with a basic understanding of the nature of biogas and challenges of producing and using it.
“A viable biogas production system can be costly and require careful management, so producers who are considering adopting this type of technology need to examine all aspects of it.”
Biogas production is based on the naturally occurring process of “anaerobic digestion” or the breaking down of organic material in an oxygen free environment.
This process takes place in an insulated, oxygen free tank or container called an anaerobic digester or biodigester. It’s within this “no air” environment that certain bacteria and other microscopic bugs excel at the handiwork of separating biomaterial such as manure into its various components.
In the case of livestock manure, this separation process results in two components –a biogas made up primarily of methane and carbon dioxide, and a slurry , called “digestate,” that is much easier to handle than the original unprocessed manure.
The biogas that is released from this process is funneled out of the biodigester and stored for use as a fuel source. While some small scale systems use the biogas as-is, other small systems and all large scale systems also use a purification process to improve the quality and consistency of the biogas. Biogas can be burned to produce electricity and heat, just like natural gas –either for use at an on-farm level or potentially for broader use.
The digestate can be used for land application as a nutrient source for crops, in the same manner as manure but with much less odour, weight and handling issues. It can also be further processed as a bio-based fertilizer that may be used on-farm or sold commercially. Reusable water can also be captured from the system.
There are many types of biodigesters, from simple small scale types to very large plant-scale versions, including some like IMUS that are part of sophisticated integrated waste management systems. The technology and approaches are constantly evolving and improving, says Navaratnasamy. “There has been a lot of progress, particularly in just the last few years,” he says. “This is helping to make biogas production a much more viable option.”
CHIPPING AWAY AT KEY OBSTACLES
There are several key challenges to broader adoption of biogas systems, but substantial progress is being made on all fronts, says Navaratnasmy.
((Bold)) Reducing payback on start up costs. For large scale systems, the main hurdle to adoption is economic feasibility, says Navaratnasamy. The capital costs of large scale anaerobic digester plants are very high and may range from a few hundred thousand to a few million dollars, depending on the size of the plant. Several North American studies have concluded the payback period can range from five to 16 years, depending on best and worse case scenarios.
However, new developments such as regulations that allow for “net metering,” coupled with funding incentives for producing green energy, can reduce the payback period significantly.
“Alternative energy has become a top issue and priority worldwide, and agriculture and Alberta are no exception,” says Navaratnasamy. “Lots of people are investing more time, research and ideas into making biogas and other new options more practical and feasible. That includes government, which is stepping up to support greater adoption.”
One solution is to incorporate additional organic materials into the biodigester that can improve the gas quality and get the digester to run more consistently –an approach called “co-digestion,” he says. “Most of the ideas that have come out on this concept are at an early stage, but we expect to see more testing and refinement of those ideas toward specific strategies in the next couple years.”
Where this issue of consistency is most common is with the recent growing adoption of so-called “lagoon digesters.” These digesters, which consist simply of a sealed lagoon rather than a typical biodigester container, are attractive as a relatively low cost biogas production option, particularly for smaller operations focused primarily on the manure management benefits.
Rising Opportunity For BioGas
At least one lagoon digester has been implemented in Alberta, and this option is expected to increase in adoption among smaller operations.
“Lagoon digesters are a good option in many cases, but consistency of energy for on-farm use can be a big issue since these systems don’t provide a controlled environment to optimize the biogas production,” he says.
Another issue for small scale digesters aimed at on farm energy is matching up seasonal energy production and energy needs. “What you may end up with is lower biogas production in the winter when you want it most, and higher biogas production in the summer when you need it least.”
Because most small scale digesters aimed at on-farm energy use are geared toward using biogas to produce heat, one option to better make use of biogas in the summer is to invest in a micro-turbine to allow for conversion of biogas energy into electricity. “This is a good option that has become more economical and effective,” says Navaratnasamy.
Article courtesy of Meristem Land & Science, Calgary, AB. Phone 403-543-7420 or visit their Web site at www.meristem.com.