[ExI] Small scale solar payback time (was Re: Planetary defense)

[Keith Henson]

On Tue, May 24, 2011 at 8:00 AM, Eugen Leitl <eugen at leitl.org> wrote:
> On Tue, May 24, 2011 at 07:41:12AM -0700, Keith Henson wrote:
>> On Tue, May 24, 2011 at 7:01 AM, Eugen Leitl <eugen at leitl.org> wrote:
>>
>> snip
>>
>> > gas network. Anaerobic digesters could cover probably up to 20%.
>>
>> I worked out trash to syngas to liquid fuel some years ago and came up
>> with less than 5% of the demand.
>
> No, I meant 20% of natural gas demand.

US 2007     652,900 M cubic meters per year

"Their largest facility,
the West Point Treatment Plant, processes 133 million
gallons per day.

"The West Point Wastewater Treatment Plant serves a 126-
square-mile area with a population of 670,000. The
anaerobic digesters at the plant produce 1.4 million cubic
feet of digester gas per day."

http://www1.eere.energy.gov/femp/pdfs/bamf_wastewater.pdf

1.4 M x 308 M/0.67 M = 644 M cf/day or 16 M cubic meters per day or
6,650 M cubic meters per year.

6,650 M /652,900 is ~1%

> The estimate being a bit
> on the high side, admittedly.

Yes, about 20 times.

Keith