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Thermal depolymerization is a process which turns solid
biomass into liquid fuels, using heat and pressure.
The process is often quoted as being 85% efficient, since
some of the liquid fuels produced must be burnt to produce
the heat needed to sustain the process.
This idea is fairly simple:
supply all of the heat using
concentrated solar power, thus allowing all or nearly all of
the chemical energy of the feedstock to become chemical
energy in the produced liquid fuel.
In a way, this is very similar to the well known process of
using concentrated solar energy for biomass gasification,
except that my idea will produce a liquid instead of a gas.
Unlike gasification, which works best with dry feedstock,
thermal depolymerization can work well with wet
feedstock, including manure, sewer sludge, algae, or offal
from meat processing plants, without needing to dry it.
Dry hydrocarbons (biomass, plastics, rubber, other
garbage) can also be turned into liquid fuels by this
process, though of course a certain amount of water must
Anything Into Oil
[goldbb, Apr 03 2011]
Crosby, Solar Tar Stills...
... and gNashing of teeth [4whom, Apr 04 2011]
||4whom, the idea you linked to is basically solar thermal
gasification, which, as I mentioned, is widely known to
exist. People were patenting ideas for it before I was
||Solar thermal depolymerization is, as far as I can
determine, an entirely new concept. I could probably
patent it if I had enough money, enough knowledge of
patents, and sufficient expectation of earning that
money back. And if I hadn't given the idea away here ;)
Gasification (whether solar thermal, or powered by the
generated fuel) turns a dry solid hydrocarbon feedstock
into a gaseous hydrocarbon fuel. In order to use
gasification to generate a liquid hydrocarbon fuel, one
must first turn the solid feedstock into a gas, then
(using the Fischer Tropsch process) turn that gas into a
liquid. If the feedstock is contains liquid water in it,
the first step of gasification is to dry the feedstock,
which requires thermal energy, and unless that thermal
energy is being supplied by the sun, requires that we
burn a portion of our generated fuel for the drying of
||Thermal depolymerization turns the feedstock (which
can and perhaps *should* be wet) directly into a liquid
hydrocarbon without ever turning it into a gas.
||Gasification uses pressures close to atmospheric, and
temperatures above 700C.
||Thermal depolymerization occurs in two stages; the
first stage (where depolymerization turns the solid
feedstock into tars) uses a pressure of about 600 psi (4
MPa) and a temperature of about 250C, and the second
stage (where hydrolysis cracks those tars into shorter,
more usable hydrocarbons) uses a temperature of about
||The temperatures required for depolymerization are
much lower than those required for gasification, thus it
should be just as easy to use concentrated solar power
to supply the heat for depolymerization as it is use solar
power to supply the heat for gasification; however, my
searches of the web does not show anyone doing so.
||//my searches of the web does not show anyone doing so//
||Possibly it is easier to use some of your biofuel, which is already quite green, to heat the biomass.
||Or maybe instead of having an array of solar reflectors, you can just let the land grow full of weeds and periodically cut it down for fuel. An acre of farmland is much cheaper than an acre of solar panels.
||Can it be that easy? There must be a catch or anyone with agricultural waste could make oil. Why would they waste their time with all the ethanol fussiness if they could go straight to oil with this scheme?
||Bad Jim, yes of course you can use some of the biofuel
for process heat, but it results in only about 85% of the
energy of the initial biomass ending up in the resulting
fuel. By using solar thermal energy, we can hope
convert 100% of the feedstock's energy into fuel energy.
If the feedstock cost money to grow and harvest, then
it's better to not waste it, when sunlight can do the job
||Bungston, people are wasting time and energy
producing ethanol from corn, in spite of it the ethanol
produced containing no more than 1.6 units of energy
for each unit of energy put into it's production... and
that's being generous, due to a combination of hype,
enthusiasm, and government subsidies.
||Assuming an 85% conversion efficiency, and ignoring the
energy costs of producing the feedstock, thermal
depolymerization can produce 5.67 times as much
energy than the process consumes.
||I would guess that the subsidies aren't as high, or the
process is newer (than either ethanol or gasification)
and less well known.