re: a composting furnace
18 mar 1999
andrew morrison wrote:
>is this for real?
seems realish to me, altho i haven't built one yet.
>can you heat your home on compost??
probably, but wood may be more convenient, and about the same price, if
you had to buy them both. last time i checked, they were about the same
price per btu, at $100 a cord and $16/cubic yard.
>can you point me to some on-line references?
you might have a look at these composting web pages:
great moments in composting:
1) the indore process (india, 1920-30), layered heaps or trenches, a labor-
intensive "adaptation and systematization of practices observed in china
and india for centuries," with a digestion period of about 90 days,
2) a modification by jackson and wad, adding half-digested sewage sludge to
reduce the digestion period to about 15 days,
3) the beccari process (italy), which used an insulated cell of approximately
20 yd^3, requiring about 40 days,
4) the verdier process, used in the french city of cannes, which added
leachate recirculation, reducing retention time to 20 days,
5) the dutch vam process (1932) for disposal of city refuse ("24 hours after
sprinkling the refuse with bacteria-rich water, the temperature has risen to
140 or 158 degrees"),
6) the frazer process (chicago) maybe the first attempt to use forced air,
which allegedly achieved "complete stabilization in 20-28 days," and
7) the earp-thomas process (new jersey), used in several cities, eg paris,
seoul, and reading, pa, in which "a vertical cylinder divided into sections
or floors forms a continuous flow digester with internal rotating booms," and
ground waste mixed with seed bacteria enters the top section, and works its
way down, floor by floor, heating as it descends, until "after 24-48 hours,
it has reached the bottom layer and the composting process is considered
by the inventors to be complete."
surely some of this engineering can be rediscovered, if we start caring about
it again. solar house heating development got stuck when we discovered cheap
oil and gas. maybe composting development got stuck when we discovered nitrogen
fertilizers, and more machines meant less manure, and people found out they
could always transport and dump solid waste "somewhere else."
a well-designed "composting fireplace" might remove 50% of the energy from
some sort of compost in a week, vs 3 months, at a rate of heat production
of something like 5kbtu/168hours-lb = 30 btu/hr-lb, so a 10k btu/hr compost
heater required 333 lb of compost at 30lb/ft^3 (50% h2o), ie 11 ft^3, eg a
3 foot cube or a 4' high by 3' diameter cylinder, refilled once a week in
a house needing 200k btu/day of heat, including hot water...