Study: biogas from manure could generate energy for millions in the U.S.
The open access paper, 'Cow Power: The Energy and Emissions Benefits of Converting Manure to Biogas', has implications for all countries with livestock as it is one the few attempts to outline a procedure for quantifying the national amount of renewable energy that herds of cattle and other livestock can generate and the concomitant GHG emission reductions.
Livestock manure, left to decompose naturally, emits two particularly potent GHGs – nitrous oxide and methane. According to the Intergovernmental Panel on Climate Change, nitrous oxide warms the atmosphere 310 times more than carbon dioxide, methane does so 21 times more.
The journal paper creates two hypothetical scenarios and quantifies them to compare energy savings and GHG reducing benefits. The first is 'business as usual' with coal burnt for energy and with manure left to decompose naturally. The second is one wherein manure is anaerobically-digested to create biogas and then burnt to offset coal (see schematic).
Through anaerobic digestion, similar to the process by which you create compost, manure can be turned into energy-rich biogas, which standard microturbines can use to produce electricity. The hundreds of millions of livestock inhabiting the US could produce approximately 100 billion kilowatt hours of electricity, enough to power millions of homes and offices:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: biogas :: biomethane :: manure :: anaerobic digestion :: United States ::
And, as manure left to decompose naturally has a very damaging effect on the environment, this new waste management system has a net potential GHG emissions reduction of 99 million metric tonnes, wiping out approximately four per cent of the country's GHG emissions from electricity production.
The burning of biogas would lead to the emission of some CO2 but the output from biogas-burning plants would be less than that from, for example, coal.
Authors of the paper, Dr. Michael E. Webber and Amanda D Cuellar from the University of Texas at Austin, write, "In light of the criticism that has been levelled against [liquid] biofuels, biogas production from manure has the less-controversial benefit of reusing an existing waste source and has the potential to improve the environment.
Nonetheless, the logistics of widespread biogas production, including feedstock and digestates transportation, must be determined at the local level to produce the most environmentally advantageous, economical, and energy efficient system, the study finds.
References:
Amanda D Cuéllar and Michael E Webber, "Cow power: the energy and emissions benefits of converting manure to biogas", Environ. Res. Lett. 3 (July-September 2008), doi:10.1088/1748-9326/3/3/034002
2 Comments:
I don't see a description of how they plan to collect the manure? It seems from the link provided that they use numbers for both indoor and outdoor livestock, but base their assumptions on the idea that all the waste will be indoor or as easy to collect as such. Being from Missouri, I know this is not the case, and definitely hope it doesn't become like this for the animals. Please tell me I am wrong.
Hi Anon,
This is a first assessment of the theoretical biogas potential in the U.S. and its potential reduction in GHG emissions when it is used instead of coal.
The paper does state, in its conclusion, that:
"the logistics of widespread biogas production, including feedstock and digestate transportation, must be determined at the local level to produce the most environmentally advantageous, economical, and energy efficient system. Other issues such as the best methods to process and distribute biogas should also be analyzed before biogas production and use are implemented in widespread fashion. Though this report has demonstrated that converting manure to biogas could make substantial positive contributions towards reducing GHG emissions if widely used, future research might consider the policy, regulatory or economic barriers to widespread implementation of such an approach."
It doesn't delve into the practical details of analysing the efficiency of harvesting, production or distribution systems. But it's certainly important to give livestock a bit of room to breathe.
Many of the scenarios on global bioenergy potentials which show very high (future) availability of biomass, are based on the assumption that livestock will be kept and raised indoor.
Post a Comment
Links to this post:
Create a Link
<< Home