Biogas

It’s a sector that has attracted virtually no attention in North America until recently, although it has reached a certain maturity in leading green tech countries like Germany and China. In fact, China leads the world in this sector with a market size of $1.7 billion in 2009. In Germany, we know of at least one established energy company that will be making a €500 million investment in the sector over the next 5 years, which would come on top of the 5000 plants already in operation across the country.

We’re talking about biogas. Others call it bio-methane, waste gas or renewable gas. Whatever you call it, this clean, renewable form of natural gas has the potential to make a significant contribution to the reduction of greenhouse gas (GHG) emissions while creating jobs and enhancing security of energy supply. It is also one of the most versatile energy carriers and can be used for generating electricity, heat and cooling purposes.

Like wind and solar power, biogas is a viable option that will be able to cover a portion of our future energy needs. The technology behind biogas exists today, with tens of thousands of functioning biogas plants in Germany, China and India, but requires further investment, research and government support to cultivate it further.

The renewable energy biogas has an important advantage in that it takes care of the climate, environment and resources at the same time. For now, the main driver of biogas in North America is GHG reduction, but what makes biogas more compelling is that it also enhances diversity of supply, provides a solution for using local waste resources to produce renewable energy, and can provide base-load electricity generation.

U.S. potential

According to a recent study, over the long term, pipeline-quality biogas has the technical potential to meet up to 25 percent of the natural gas demand in the Northeastern U.S., not including natural gas demand for power generation. That is enough energy to meet the annual demand of approximately 2 million homes that use natural gas for heating in the Northeast. All of the feed-stocks considered in the study for the production of renewable gas are sustainable. This was done to avoid the issues that have come up with ethanol production, which impacted the broader food industry.

Renewable gas is essentially upgraded biogas. It refers to pipeline quality gas derived from biomass that is injected into the natural gas distribution network for direct use in existing natural gas appliances and power plants. Yes, it is fully interchangeable with natural gas. To date, direct injection of renewable gas has been limited to a small number of projects in the United States. For example, the Fresh Kills landfill in Staten Island, New York has been operating for almost 30 years providing 1.8 billion cubic feet (Bcf) of pipeline quality gas annually. In addition, there are a few individual farms and waste water treatment plants that have utilized clean-up technologies to make compressed natural gas (CNG) for vehicles.

The current state of biogas in the U.S.

Currently, most producers either flare (i.e. burn off) the raw gas or utilize it in a generator to produce electricity. This raw gas (biogas) is composed of roughly 50 to 60 percent methane and 40 to 50 percent carbon dioxide (CO2). Flaring the gas converts methane to CO2 thereby reducing the GHG effect by a factor of 20.

Renewable electricity incentives in certain U.S. states have led to a proliferation of power generation projects at landfills, waste water treatment plants and some farms, but using this gas to produce pipeline quality gas is a more efficient way to utilize the energy.

The advantages of renewable gas

Producing pipeline quality gas allows you to utilize almost all of the energy in renewable gas, whereas electricity-generating power plants often have to let the process heat escape into the atmosphere.

In addition, one of the drawbacks of using biomass for power generation is the air permitting process, which can be complex and lengthy. Biomass emits either methane into the atmosphere when it is decomposing or carbon dioxide when it is digested and flared. By collecting, conditioning and injecting a high percentage of the available methane into the natural gas network, customers can directly use the gas in their existing natural gas appliances and other end-use applications.

Further, renewable gas reduces GHG emissions by fuel substitution, essentially switching from a fossil fuel to a renewable fuel. Using renewable fuel represents the recycling of carbon already circulating in the environment, and using fossil fuel represents new emissions of carbon that was previously trapped geologically beneath the earth.

Renewable gas for transportation

Through the use of biogas as a fuel in the transport sector, it is possible to greatly reduce carbon dioxide emissions when compared with fossil fuels. Biogas is almost CO2 neutral, since the energy plants take up the same CO2 amount in their growth phase as is released upon production and use. A Biogas plant requires roughly 15 to 20% of the total energy it produces for transport and production. In other words, for every unit of energy invested in the process, one receives 4-5 units of energy. This is a better return on energy investment than tar sands.

Other than the revenue generated through the sale of biogas, there is the added advantage that the fermentation remains are less caustic and can be used on agricultural fields as fertilizer, leading to greatly reduced ammonium and nitrate in the ground water, and do not have any dangerous bacteria.

Virtually any production of biogas at any time at any place can be accommodated, as long as it takes place near a natural gas grid with enough capacity. The fed-in biogas can be sold there where it provides the best returns, rather than simply at the point of production. The use of biogas is very efficient, since all current natural gas technology (petrol stations, gas burners/heaters, etc.) can use the upgraded biogas without further changes. \

Biogas plant south of Hanover, Germany: http://www.bbfm.de/

The basic science behind biogas

Raw biogas is created through the fermentation of organic material in sludge (biomass), where bacteria destroy the material. Biogas therefore comes out of biomass, which itself comes from plants which grow with the help of sunlight. In addition, these plants absorb elements from the atmosphere (e.g. carbon dioxide) and the soil (e.g. water and minerals), and transform them through photosynthesis. The biogas process is only one of many different transformation technologies that exist to convert biomass into a form of usable energy. Biomass can also be converted into a usable form of energy through burning, gassing and liquefaction.

In the case of biogas, a biochemical conversion technology is used that breaks down the organic material an-aerobically (i.e., in the absence of oxygen or light). The methane bacteria which break the material down are active in a temperature range of 0-70°C, but generally, a higher temperature leads to a faster fermentation process, which in turn leads to a higher biogas production.

Biogas’ advantages over other biomass conversion technologies, including ethanol

It must be explained here, that the biogas process has a great advantage over other biomass conversion technologies such as burning, gassing and liquefaction. Since fermentation occurs at only slightly higher than outside temperatures and the biogas separates on its own, the energy demand is very low when compares to the other conversion technologies. These conversion technologies often require multiple steps and much higher temperatures, leading to increased energy demand.

This biogas process has important advantages: 1) it leads to a good gas output, which reduces the atmospheric impact (no escape of methane); 2) the biogas tanks can capture any remaining gas from the remaining substrates, as well as reducing any possible smell problems; 3) nitrogen-losses are minimal, thanks to the sealed silos, leading to higher quality fertilizer for agricultural purposes.

“Anaerobic digestion can unlock significant benefits from animal waste – the resulting byproducts are better fertilisers than the raw feedstock.” Source: http://www.ifandp.com/

In addition to waste gas from large city garbage dumps, the cultivation of grass and corn is also possible to produce biogas. Used to raise biogas output, energy plants have additional advantages:

1) Proven production techniques exist, since energy plants use similar cultivation techniques to normal silage. Energy corn has a later harvest date than standard corn (3-4 weeks) and requires less fertiliser.

2) Energy corn can be fertilised with fermentation remains. Experiments have shown that corn can be cultivated in a manner that protects ground water in sensitive areas.

3) Energy plants are a clean raw material, can easily be used in the biogas process and allow for a closed nutrient cycle.

Biogas production aids agricultural processes

The resulting mix of fermented dung and energy plants is, thanks to the breaking down of caustic organic acids, much friendlier to the environment and crops. Slimy and fibrous materials are also broken down, so that the fermentation remnants end up quicker in the soil, reducing methane and ammonium losses. This increases the actual fertiliser effect, since the ammonium is immediately available for the plants.

This gives it a big advantage over conventional organic fertiliser, since the fertiliser effect of the nitrogen in the fermentation remnants is easier for the farmer to measure. This in turn leads to nitrate savings when fertiliser has to be brought out on the fields, which then leads to a positive effect on the ground water quality.

Finally, the fermentation of dung also reduces the smell problem when its remnants are brought out on the fields.

The future for Biogas in the U.S. and around the world

If the U.S. decides to take full advantage of the biogas potential in the country, electric utilities would notice. Some studies peg the U.S. potential at around 8000 anaerobic digesters, for a total generating capacity of 1500 MW, or 2% of all electricity production. This would be production with a capacity factor near 100%, meaning renewable base load power.

Feed-In Tariff (FIT) schemes are in place in California, Florida, Vermont and Hawaii, and states such as Wisconsin, Indiana, Michigan, Minnesota, Maine and Washington are considering them. Walmart recently announced its decision to install 400kV fuel cell units supplied by Bloom Energy at two stores in Southern California, with the goal of running both on biogas.

In China, nearly 30,000 biogas plants supply 40 million households with clean burning biogas, a huge improvement over the burning of wood and animal waste for cooking and heating. According to reports, China is looking to supply 300 million rural residents with electricity generated from biogas by 2020. This will require a growth rate of roughly 9% annually, and triple the amount of biogas being produced in China in 2020, when compared to rates in 2000.

Efforts are also underway in Africa, where governments see biogas as a way of reducing deforestation. In Tanzania’s Makete District, 200 biogas plants will be constructed. According to the government, on average, a flock of two cows or seven pigs or 170 poultry is sufficient to provide enough biogas for a family’s cooking and lighting needs. In Kenya, a five-year piloting project is taking place, with the goal of developing 8000 domestic biogas plants in rural areas.

In Europe, other than market leader Germany (covered above), Sweden, Italy, Denmark and Poland have announced plans to increase their biogas markets substantially. Plans in Denmark include the construction of what will be the world’s largest biogas facility.

As is clear to the reader, biogas looks set to enjoy substantial, sustainable growth over the coming years. Leading countries, both developed and developing, have plans and policies in place to support the technology, and electricity and energy developers will be joining the push.