Category: Combined Facilities


Biomethane as an Energy Carrier -  Superior to Electricity!

October 20, 2009

Methane is a better long-distance energy carrier than electricity. Its storage and transportation is much cheaper and easier than electricity. Natural gas pipelines cost half as much to build as electric towers and have about one fourth as much transmission loss. They are also more reliable, safer and visually superior to ugly transmission towers….

Our electrical grid is only 30% efficient in delivering the energy in fuel burned to the customer. That efficiency could be doubled or even tripled if we used combined heat and power (CHP) generators located where heat is needed. By using the generator’s waste heat, an efficiency of 85% is possible. Clearly it is smarter to expand our gas pipeline network than to build more electrical towers to distribute inefficiently generated electricity from massive power plants. …

In Germany 22 billion kWh of biogas were produced in 2007. That’s a six-fold increase from 1999, driven partly by feed-in tariffs. About half of that biomethane was from landfill and sewage gas and the other half was from commercial and agricultural biomass plants. Renewable biogas is produced by natural processes of anaerobic digestion or gasification then cleaned up for sale to the gas pipeline. Sweden already gets 25% of their energy from biogas.

Energy storage is another big advantage of gas. Both the gas and the electricity grids need energy storage to take up the slack between production and consumption. Gas storage is cheap because it can simply be pumped into depleted gas wells and salt caverns. We are already storing 4.1 Tcf of gas in the US. At 85% efficiency that gas could produce 1,180 gigawatt-hours of useful power on demand. A very cheap battery!  The smart electrical grid is all about making supply match demand because electrical storage is so expensive. …

People have already begun selling renewable gas into the pipeline.  Landfills, manure piles and sewage plants that used to release significant amounts of methane into the atmosphere are now selling it as green gas. Biomass and garbage can also be gasified to add to the supply. The energy balance of Grass Biomethane production is 50% better than annual crops now used. When biogas is captured instead of releasing it to the atmosphere we get a double bonus. Methane is 72 times worse than CO2 as a cause of global warming in a 20-year time frame. You may have heard 25 times, but that’s based on a 100-year time frame. Methane only persists about 8 years. Also, when manure piles are covered, N²O, which is 289 times worse than CO², can also be captured. Coal mines emit almost a trillion cubic feet of methane into the atmosphere every year.

In Cincinnati, Ohio, the 230-acre Rumpke landfill has been capped and the gas is cleaned and delivered to the pipeline to provide enough gas for 25,000 Duke Energy customers. China has an estimated 31 million biogas digesters mostly on small farms. They produce in total about 9 Gigawatts of renewable energy which is mostly used locally. Germany, Denmark, Sweden, Finland and now Ontario, Canada have feed-in tarrifs to encourage production of biogas. In Germany small farms can receive up to 25 cents per kWh for biopower. In the US, bills like SB306 that support biogas production, are still stuck in committee.

Image courtesy of : http://www.grt-inc.com/go/strategy/feedstocks/biomethane/

Increased system efficiency means we will need less of these renewable sources to do the job. If we’re going to gasify biomass, it is more efficient to upgrade the gas and send it through the gas grid to customer CHP units than to generate electricity less efficiently and send it over less efficient, more expensive power lines to the customer. Until we get more efficient electrical generators, generation should always be done where the waste heat can be put to good use.

Electric cars would be twice as efficient if they fueled up with natural gas and used a fuel cell to recharge a small battery. Like a hybrid with a natural gas fuel cell range extender. The expense and weight of a large battery is eliminated and the energy can be stored in a much lighter and cheaper tank. Refuelling can be much faster and could even be done at home from your natural gas connection. New, low pressure, adsorption tanks make this easy because they only require 500 psi of pressure. Recharging is a problem with batteries.  A 110v, 20A household plug can only supply 2.2 kW, which means that 10 hours of home charging will only take you 10 x 2.2 x 4 mi/kW = 88 miles. Natural gas refueling infrastructure is in place in much of the world to refuel five million vehicles worldwide.

More:

http://cleanenergy.multiply.com/journal/item/127/Biomethane_as_an_Energy_Carrier_-_superior_to_electricity

In an article posted May 13, 2010, the Addison Independent reported that Vermont’s Middlebury College entered a preliminary agreement with Integrated Energy Solutions (IES) to introduce biomethane into the college’s portfolio of heating fuel. The project is still in preliminary stages, but it will swap up to 650,000 gallons of fuel oil each year for biomethane gas produced from manure collected from local small dairy farms. Plant wastes may also be incorporated.

The wastes will be combined and fed into a digester to produce biomethane gas which will be burned to generate boiler steam to heat campus facilities. Biomethane may also be used to produce electricity for the college.

For more information, see:

http://www.addisonindependent.com/201005college-add-farm-methane-fuel-mix

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