17 Feb 2009
Once again DEFRA are behind the times and miss the point.
Sure, manure and slurry are great as part of the feed stock for digesters but ideally they would use 15% animal wate and 85% plant or food waste. Since, economically, it isnt "worth" investing in anything but the best then livestock farms woulod have to export all thier waste or import 5 times that amount of plant matter/ food waste. Niether export nor import are acceptable since farms are as busy as can be already and the existing infrastrucure would not be able to cope with the extra traffic.
What Dr. Scurlock nees to address is implementation of digesters that accept an unbalanced feed.
There also needs to be considerable investigation into the nutritional effects of AD regarding fertilizer and biodynamic qualities of the material output.
20 Feb 2009
I think you are being hard on Defra for this one. They are pushing for widespread adoption of anaerobic digestion which should be commended as a strong move. Anaerobic digestion is a valuable technology which offers renewable domestic energy source whilst dealing with the problems of climate change.
I agree there are definately benefits to the co-digestion of food waste along with slurries. Co-digestion of energy crops is also a viable alternative to food waste. Transportation costs vs dewatering and nitrates should also be considered when determining whether AD is the right technology for a given source of manure.
There have been many studies into the nutritional effects of digestate as a fertiliser. The BSI PAS 110 is currently in draft format and seeking sign-off from the EU. This in turn follows on from the widely adopted German RAL-256 standard. Digestate offers an excellent alternative to chemical fertilisers.
23 Feb 2009
The National Grid are considering Biogas, anaerobic digestion has been around for years, see whose technical director runs his house on grass digestion, in 1955 there were about 55,000 digesters on Indian farms, a pig farm near Birmingham operated with one, including for all swill boiling
Given below are a number of websites which give considerable information on the whole subject