New Web Site from Xergi Biogas Provides Insight Into AD Life Cycle Assessments
Xergi - The Biogas Plant Contractor, contacted me recently to announce their new web site. I like the site a great deal, and in particular I recommend their downloadable Life Cycle Assessment report which looks at the relative whole life environmental benefits of different Anaerobic Digestion feed stocks.
The report is titled:
Life Cycle Assessment of Biogas from Maize silage and from Manure - for transport and for heat and power production under displacement of natural gas based heat works and marginal electricity in northern Germany
Please note that the Life Cycle Assessment is being reviewed. The final Assessment will be issued after completion of review, we are told.
However, the report is published in its 2nd draft, dated June 21st 2007. The authors are Kathrine Anker Thy° and Henrik Wenzel of the German Institute for Product Development.
An extract from the summary follows, but there are a lot of data and other information in this free report, making it worth a visit to their web site at the link below, for anyone seeking to decide which are the greenest options for AD plant projects.
Biogas based on manure is not an alternative strongly correlated to the other bioenergy scenarios, because it does not include any utilization of agricultural land. However, since it provides the same services to society as the other scenarios, it still compares to them and should b included in the overall prioritisation of which type of bioenergy technology society should promote with subsidies and other incentives.
The conclusion of this comparison is unambiguous: biogas from manure implies by far the highest reduction of greenhouse gas emissions per unit of services provided to society. This being due to the fact that it implies CO2 reductions not only from the fossil fuel replacement by the generated biogas, but equally significantly from the reduce methane emissions from manure storage, reduced nitrous oxide emissions from soil application of the manure and improved plant availability of the nitrogen in the manure.
The brief and overall conclusions on manure based biogas can, thus, be expressed as:
- Biogas from manure stands out as having much higher reduction in greenhouse gas emissions than the other bioenergy types and equal savings in fossil fuels. As cost aspects point to the same direction, manure based biogas should have the highest priority of all the compared bioenergy types.
The other scenarios are strongly correlated by their competition for the same agricultural land. Based on the comparative approach, the LCA shows that environmentally and in terms of fossil fuel savings, energy crops should be prioritised for heat and power purposes either 1) through a preceding biogas generation or 2) by direct incineration or gasification, these pathways leading to almost equal CO2 reductions and fossil fuel savings. Energy crops converted directly into a transport fuel implies significantly lower CO2 reductions due to the energy losses in the conversion processes.
The brief and overall conclusions on maize based biogas can, thus, be expressed as:
Among the compared types of bioenergy requiring agricultural land and energy crops, biogas from maize silage and heat and power from willow imply the highest reductions in greenhouse gas emissions and the highest fossil fuel savings, environmentally and in terms of fossil fuel savings.