Thai Biogas Plant Visit, a First...

As part of the WREC (11th world renewable energy congress) conference i've been fortunate enough to attend over the last few days, today i got to visit my first real biogas plant...

One of 4 sites belonging to the Thai Biogas Energy Company, this plant in Saraburi produces 900 kW a day from industrial waste stream piped in from a cassava processing plant (which produces starch).

The biogas plant processes about 3,000 cubic meters of sludgy waste stream per day. The mixed sludge (so that it's more uniform) is basically treated and put into a big "lagoon" (about 9 meters deep), and covered with a black, tarp-like plastic. As the sludge decomposes (ie, "anaerobically digested), the tarp bubbles up with the methane emitted. About 60% of these emissions are methane (which are 21 times the value of CO2 per tonne!). That's quite significant when you start talking CO2 credits...

The gas is sucked through another pipe, then filtered (i'm gonna skip that explanation for brevity's sake, pressurized, and then converted into electricity with an expensive General Electric gas turbine (another explanation i'll gloss over...!).

Of the 900 kW produced daily, the plant uses 100 of it, then supplies the cassava processing plant with 600 kW (100% of its power needs), and sells 200 kW back to the Grid.

For perspective: the average power usage in the american home is 1000kWh per month (= 1 megawatt-hour/mo). If you've got a couple of computers, TVs, etc - maybe you're looking at 1200-1500 kWh/month...

Rounded residential costs:
$.12/kWh in FL;
$.18/kWh in MA;
$.13/kWh in CA and DC.
(source: 1/2009 data release by US govt EIA in 4/2009).

If you've gotten this far without glazing over, thanks - the plant was about 2 hours out of bangkok, next to a lush river, and a little stinky, though not as stinky as municipal waste would ... and now i'll move on...