ray chrisman, university of washington,...
TRANSCRIPT
Developments in the Preparation and Use of Bio‐Char
Ray Chrisman, University of Washington, USA
Direct
measurement
of carbon
dioxide
indicates that
the level has
definitely
been rising
for the last 50
years though
variations in
concentration
are a natural
event.
Natural fluxes of carbon dioxide are very large but data indicates that the current increase is related to fossil fuel consumption
Carbon dioxide is
the most abundant
greenhouse gas but
emissions of other
gases are
significant
contributors and
any reduction in
their emissions will
be helpful
There are basically two approaches to cut the level of greenhouse gasses; reduce
emissions or capture and sequester them
Sequestration side of the CO2 issue
Stabilizing CO2
at 400 ppm requires approximately 35 GT CO2
(~10 GT carbon)
to be withdrawn from the atmosphere by 2030
http://www.vattenfall.com/www/ccc/ccc/577730downl/index.jsp
The question is how can it be done and where can we put it? In the water or on the land?
Production and use of biochar can be a significant component of a CO2
sequestration program
•
AgricharTM product is
derived from Slow Pyrolysis
which involves heating
biomass in the absence (or
reduced supply) of air •
AgricharTM product delivers
significant agricultural and
environmental benefits –
whilst sequestering carbon
in soil
How BioChar
can enhance the lifetime of land sequestration of carbon
100
50
10
1 32
Bio-char
Un-charred organic matter
4 5Years
Car
bon
rem
aini
ng (%
)
Lehmann et al., 2006, Mitigation and Adaptation
Strategies for Global Change
Terra‐Preta: Evidence of longevity in the soil
•
500‐7000 years old
•
Amazon ‐
Extreme
environment for fast
organics turnover
•
10% Total Carbon, 35% of which is Black Carbon. Char ≈
3.5% of total soil.
Photos: Julie Major, Cornell University
The ‘terra preta’ example of improved plant growth
It can reduce soil release of nitrous oxide by 80% and completely suppress soil release of methane
Thus the good news is that the use of biochar
not only sequesters
carbon, it also reduces other greenhouse gas emissions and it
improves plant growth
Even better, the biochar
process is a co‐product process for energy and
biochar
Biochar a Gigaton response
Source: Lehmann, 2007, Nature
-20
-15
-10
-5
0
5
10
Gt C
arbo
n
Annual potential for biochar
sequestration
Hypothetical(40% biomass to
biochar)
High
Low
Gaunt unpublished
Biochar
appears to have positive environmental features
However, if we are going to put billions of tons of this material in the
soil we had better have a good understanding of the potential impact
Bulk composition of a typical biomass material. Depending on
heating rate the cellulose crosslinks
or depolymerizes. Final
temp (low) aliphatic rings or (high) aromatic rings
Biomass also has the following components
•
Extractables
such as resins, starches, waxes, lipids, hydrocarbons and various phenolics
which in total are only about 1‐5% on a dry basis.
•
Water
•
Ash which is the metal ions and silica. Ash can vary from 0.5% for most woods to over 20% in cereal grains. Can cause process and product
problems
IBI conference 9/08
Almost any time biomass is burned in nature both pyrolysis
and oxidation occurs
Often both processes occur such that oxidation (burning) is on the outside and provides the heat for pyrolysis
which is going on inside. The
biochar
that first forms is then burned when oxygen can finally reach it.
For example, the burning of cigarettes
How do we get just biochar?
There are many variations in pyrolysis
for the production of energy and biochar
The energy co‐product is derived from the smoke. Careful processing
can be used to produce enough energy to help reduce the need to
burn fossil fuels
Without processing the smoke is a source of gases that have a higher greenhouse effect than CO2
The pyrolysis
processes typically produce three general product types based on physical state
•
A gas that is mostly syn‐gas (H2 and CO) with some light hydrocarbons
•
A complex hydrocarbon liquid (bio‐oil) and water
•
A solid char (primary and secondary) and ash
The relative yields and composition of these products are a function of process conditions
and starting materials.
These liquids need to be captured and not allowed to condense on
the char
Properties of biochar
are a function of processing temperature and starting material
BEST’s
Australian Demo facility
•
Fully continuous with
Integrated drying
•
Handles biomass with up to
50% moisture
•
Can process high and low ash
biomass
•
Syngas
produced runs 300
kWe
internal combustion
engine
•
Approx. 35% yield by weight
•
Can be scaled to process 48
& 96 dry ton/day
IBI conference 9/08
The integrated continuous process can alter the ratio between biochar
and energy production
What is Agrichar
TM
biochar?
•
AgricharTM product is derived
from Slow Pyrolysis
and is a
primary char which means it
maintains much of its
original physical structure.•
This structure seems to
support enhanced microbial
growth, aid in water
retention and enhanced soil
structure.•
The material has good CEC
and has a long lifetime in the
soil.•
The material has no odor and
low residuals.IBI conference 9/08
The
water retention feature is a key reason the UN is promoting
the use of biochar
to combat desertification
Distributed manufacturing model for biochar
from dairy manure
•Dry manure to 50% solids before transport to facility; fresh is
165lb/day/cow, 12% solids. Reduces methane emissions from
current storage approach•Collect manure from dairies, 260 sites indentified in US with
the needed 12,700 cows within 30‐50 km of a potential facility•Operate 96 tpd
dry basis feed to co‐produce energy and
biochar•Export energy to local user; grain dryer, milk processor, etc.,
potentially 47 trillion BTU/year for rural use•Sell biochar, 750 million pounds•25‐30% internal rate of return depending on product mix
The project was supported by the Small Business Innovation Research program of the U.S. Department of Agriculture, grant number 2008-33610-18876
There are a significant number of uses for biochar depending on performance properties of material produced
The project was supported by the Small Business Innovation Research program of the U.S. Department of Agriculture, grant number 2008-33610-18876
Additional potential Environmental benefits from biochar
usage
•Biochar
has been demonstrated to capture metals (Lima, USDA). Potential to
filter water from mine tailings•A program being developed to clean
farm runoff to reduce nitrates, phosphates and herbicides (Allred, USDA)
Summary of potential benefits of the biochar
process
•Sequester Carbon Dioxide•Generate energy•Solve some waste management issues like
disposal of manure•Improve soil quality
This program is no where near the 1 gigaton range needed to have a significant impact on CO2
emissions but it could be a cost effective start