[Terrapreta] Charcoal in Compost? 4USA?

[Tom Miles]

Sean,

 

The objective of systems like Advanced Biorefinery, JFBiocarbon, Renewable
Oil, BEST, and several others listed on the TP website is to be either
mobile, portable or central to sufficient resources for conversion to energy
products such as oil and char. Typically you see proposals to export the gas
as electricity after being burned in an engine or a combustion turbine.
Portable pyrolyzers have been demonstrated for more than 30 years. In my
experience none of them have been successful. It's a cash flow problem: you
don't generate enough revenue at the portable scale (25-50 tpd biomass) to
pay the salaries of the operators, let alone the capital and operating
costs. Since 1965 we have designed portable sawmill equipment that has been
used  in thousands of locations around the world. In most cases the portable
mill is set up and runs as a virtually permanent, but lower cost, mill for
years. It is always cheaper to move the material to the mill even where
transportation fuels are high cost, like remote Alaska. The smallest modular
plant that you are likely to see is probably 50 tpd which is a scale that
Advanced Biorefinery and BEST are promoting. 

 

A more practical industrial processing scale is 250 tpd or more (~$15
million?). This becomes a fixed plant fed by 40 or 50 contractors. The total
cost of processing biomass to energy and char product will probably be about
$100/ton of dry biomass. If you only produce one product, char, at a yield
of 20%, then you need to recover $500 from each ton of char ($100/.2 ton=
$500/ton). If the char can be a byproduct of oil, gas or power production
and only has to pay for its portion (20%) of the input biomass  then the
costs attributed to the char are only $100/ton ($20/.2 ton).

 

Municipal and agricultural biomass residues are never "free."  Typically it
costs up to $30/dry ton to harvest and roadside field crop residues, forest
slash, or construction debris. Then it costs another $20/ton to haul the
residues to a use or disposal point. So the total cost of the biomass
delivered to the processor , i.e. pyrolyzer, can be $50/dry ton. In some
cases the $50/ton is paid by the home owner or developer. In many cases it
is a cost that must be borne by the end use such as fuel or fiber. Add
another $50/ton for processing (and packaging)  and you're at $100/ton. I
think that will be about the minimum ex plant cost for bagged charcoal
products. So a retail, or a delivered, price will probably be in the
$200/ton range. That's what we're paying for similar soil amendments. 

 

In my area we process forest residues, construction residues and field
residues. The costs I used above are similar to our costs for forest
residues and for agricultural residues. Our contractors that are cleaning up
fiber in the forest under stewardship contracts are fortunate that we
currently have pretty good markets for small logs and low quality chips to
help pay for the cost of residue removal. The state of Oregon now offers
$10/ton for biomass use which helps offset harvesting and transportation
costs.  We try to find sites where there is enough "solid wood" in residues
to recover higher value products to help pay for the residue removal. After
solid wood processing about 50% of the wood is still available for energy
and char.  

 

In agriculture we have 2.5-4 tons of removable straw per acre from our
perennial grass seed cultivation. We harvest the straw and repackage or
"process" it for export. We've been doing this since 1974 so we have a
pretty good idea about costs. This year we exported 740,000 tons of straw
(from 400,000 acres) at a price delivered to the port of about $100/ton.
That includes only about $5/ton for profit. To harvest and process the same
straw for charcoal will probably cost about $100/ton. Most of the grass seed
crops are perennial so the charcoal wouldn't be used on the same field until
it is re-established (3-5 years). We don't grow much in the way of row crops
such as corn. The charcoal would be used in horticultural crops or in urban
landscaping. To be used it would have to show a benefit in horticulture, as
you saw at Fourth Corner Nurseries,  or in landscaping.

 

Put some real numbers on the energy costs (gal oil/ton char, electricity,
etc.) of harvesting and processing and I think you will be surprised.  There
has been a lot of modeling of energy consumption in harvesting and delivery
in the USDOE Feedstocks program. 

 

Tom

 

 

From: Sean K. BArry [mailto:sean.barry at juno.com] 
Sent: Monday, July 09, 2007 11:24 PM
To: Tom Miles; 'Bernie Lenhoff'
Cc: terrapreta
Subject: Re: [Terrapreta] Charcoal in Compost? 4USA?

 

Hi Tom, Bernie,

 

How much biomass waste is transported to and received at a municipal compost
site?  Could the biomass be processed into charcoal on site, in the place
where it grew, and tilled in to that soil?  The $200/ton cost for charcoal
from "free" biomass waste should not cost that because of the transportation
fees of either the feedstock, nor the product distribution.  Processing
plants will need to be many and mobile.  Preferably, the whole biomass
gasifier/pyrolysis reactor/charcoal kiln system will be transportable on,
and run entirely on biomass based fuels and energy.  The Germans and these
Swedish Drs. Fischer & Tropsch had transportable wood to fuel systems, that
made liquid transport fuel from biomass on site.

 

Small, efficient, transportable systems will be far less expensive than
large processing plants, or heavy tpd compost processing lots.  Capacities
will be small # of tons per acre-day or small kilotons per acre-year.  A
system like this will process biomass and deliver the product without the
cost of transport of either.  Right now, the most reliable source of biomass
is distributed everywhere.  Transport of it would be the primary cost of
acquiring most of the waste biomass for a large processing plant.  Transport
to any application site & application of the product will be most of the
cost (fuel costs) of delivering any charcoal product made in a large,
centralized, biomass processing plant.  One of the presumed "best" places to
apply charcoal is agricultural soil, to partake of the "Terra Preta"
phenomenon to improve the ability of the soil to hold its fertility and
promote the growth of plants (including valuable agricultural food and
energy crops).  There is agricultural waste on most acres of agricultural
land every year, for a time.

 

Application of the charcoal made from plants and into the soil they came
from is easy.  The ancient Amazonians were not likely transporting biomass
or much charcoal.  At least not large amounts very far.  Pyrolysis was done
on the spot, in the land intended to be used for crops.  It is obvious that
conversion of biomass to charcoal, for use in soil, is done on the soil,
with the standing biomass whenever possible.  It certainly should be a less
energy intensive and subsequently less expensive methodology, than large
centralized biomass to charcoal processing plants.

 

It should be noted that the energy inputs required for processing biomass
into charcoal, are most likely only just met by the producer gas BTU content
and waste heat.  There is likely not enough energy to transport the biomass
around a lot or over long distances.  The tractor fuel gathering waste
biomass in a field may also not be supplied by enough fuels produced in the
pyrolysis reaction.  Wood chippers run on liquid fuels.  When biomass is
pyrolyzed to obtain a higher yield of charcoal, then there is less "producer
gas" and less bio-oil released, so less to be extracted from the reaction.
It will be harder to make a biomass processing system energy efficient, when
transport costs are involved.

 

Regards,

 

SKB

 

 

----- Original Message ----- 

From: Tom Miles <mailto:tmiles at trmiles.com>  

To: 'Bernie Lenhoff' <mailto:bernie at greenwasterecycleyard.com>  ;
terrapreta at bioenergylists.org 

Sent: Monday, July 09, 2007 6:40 PM

Subject: Re: [Terrapreta] Charcoal in Compost? 4USA?

 

Bernie,

 

California has had pyrolysis demonstrations in the past but none of them has
demonstrated using char in agriculture. What would it take to demonstrate to
landscapers and nurseries in your area that char would be useful to them?
The nursery next door making saving money or getting better production by
using char? Where do we start this process?

 

One 50 dry tpd plant would produce about 10-15 tpd char plus oil and waste
gas. Gas from the process would be  used to make the oil and char. 

 

A char product could go out as 10%-20% in blended planting mix products or
as char to agricultural applications. At concentrations of 2-4 ton/acre a
day's production would cover 2.5-7.5 acres; 625-1875 acres per year.   

 

Delivered planting mix products are about $200-$250/200 ft3 unit around
here. Pick $200/ton as a price and you have a gross char sales of
$2,000-$3,000 per day; $40,000-$60,000 per month. Char production would be
2500-3000 tons per year. 

 

It sounds like as a biomass producer you'd rather sell to a char and oil
processor rather than produce the char yourself. How do we get the guy next
door to build a charcoal plant? 

 

Regards,

 

Tom

 

 

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