Dairy manure to energy Opportunities disguised in challenges

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Dairy manure to energy Opportunities disguised in challenges Powered By Docstoc
					                                                                                                                                              March 2008
                                                                                                                                              Vol. 8, No. 1

                                                                      for the West, about the West, from the West

Dairy manure to energy: Opportunities
disguised in challenges
By Saqib Mukhtar,                                     Combustion
 Extension Agricultural Engineer                         Dairy manure as a fuel has the po-
 Texas A&M System                                     tential to be burned directly. However,
                                                      scraped manure from dirt lots or ma-
I ncreasing world demand for energy and               nure mixed with sand bedding has a
the high cost of oil and natural gas have el-         higher ash content (inorganic residue
evated interest in alternative and renew-             such as soil or other inorganic materi-
able energy sources such as biofuels,                 al that remains after combustion)
forests, wind, solar and animal manure.               than other biomass (e.g., wood and
While demand for hydrocarbon energy from              straw) or fossil fuels (e.g., coal). There-
crude oil, natural gas and coal will continue         fore, direct combustion of manure is
to rise, renewable energy will become more            not practical and efficient, and it is
important in coming years.                            desirable to mix it with other less
   Researchers are looking for alternate              variable fuels.
fuel sources to replace fossil fuels and                 One means of doing this is co-fir-
many are focusing on animal                                           ing, which refers to mix-
manure as a renewable energy                                          ing dairy manure and
source. Dairies have grown in         Opportunities exist for         fossil fuels in conven-
size and in some regions their         converting manure to           tional power plants. Sig-
high concentration, limited            syngas on-site or on-          nificant reductions in
surrounding crop or pasture                                           emissions from sulfur
                                      farm. Small and modu-
land, or soils high in phospho-                                       dioxide (SO2) – an air       A recent grant from the USDA Natural Resources Conservation Service
rous (P) may require reduced            lar gasification and          pollutant released when (NRCS) is funding assembly and testing of a portable anaerobic digester and
amount of manure application            anaerobic digestion           coal is burned – are         gasifier system at the Biological and Agricultural Engineering Department
                                                                                                   at Texas A&M University.
on adjoining farmland. This              units could be in-           achieved with co-firing
reduced use of dairy manure                                           systems in power plants                    rally occurring microorganisms (bacteria)
                                       stalled on the facility
as a nutrient source for plants                                       that use coal as fuel.                     in the absence of air (especially oxygen) to
may require either increased          to eliminate issues as-            Transporting a low-value                produce biogas. Biogas, which is produced
on-site manure storage, or its          sociated with trans-          product such as manure over                from degradation of organic matter in ma-
transport and application to           port of high moisture          long distances is expensive, so            nure by the bacteria, contains primarily
cropland at greater distances                                         using access dairy manure as               methane (CH4) and carbon dioxide (CO2).
                                          manure off site.
from the dairy operation.                                             a co-fired fuel source instead             Other gases, such as nitrogen , hydrogen
   Dairy producers facing this                                        of as a fertilizer could save              sulfide (H2S) and trace organic components
challenge will benefit from opportunities             not only money but also the environment.                   are also present in relatively small quanti-
that enable economically moving large                    Small-scale studies at Texas A&M Uni-                   ties. Typically, 60 to 65 percent of biogas is
amounts of manure off site, or utilizing it           versity show that co-firing of manure with                 CH4. Methane and CO2 represent more
beneficially on-farm. To meet these man-              coal may also reduce nitrogen oxide (NOx)                  than 90 percent of biogas.
agement challenges, engineers and scien-              emissions from coal, which also contribute                    Methane produced from anaerobic diges-
tists with Texas AgriLife Research, Texas             to air pollution.                                          tion and utilized as a source of energy also
AgriLife Extension, and Texas Engineering                                                                        reduces its natural emission, which has
Experiment Station are exploring different            Anaerobic Digestion                                        much greater global warming potential
options of converting manure to energy.                  It is the treatment of manure with natu-                than CO2. The heating value (energy re-

                 Western Dairy News is a collaborative effort of Dairy Specialists from:

March 2008                                                                                                                                                            W-51
leased from a given mass of a fuel) of biogas    on the facility to eliminate issues associat-             be taken from farm to farm for educational
containing 65 percent CH4 is approximately       ed with transport of high moisture manure                 demonstrations.
600 BTUs per cubic foot (ft3). For compari-      off site. Dairy operators could build these                  Essentially all manure-to-energy conver-
son, 1,000 ft3 of biogas with 65 percent CH4     systems to process and convert part of their              sion processes will result in residues that
will be an approximate equivalent of 600 ft3     manure streams, such as separated solids                  will be reduced in volume but might not
of natural gas, 6.6 gallons of propane and       or composted manure, to produce auxiliary                 have immediate value. For instance, most if
4.7 gallons of gasoline.                         energy and power, including bio-fuel for                  not all of the plant nutrients will remain
                                                 farm use. As they learn to work these sys-                following anaerobic digestion. Also, char
Gasification                                     tems they could add more units and in-                    will be produced by the gasification process.
   This is the process by which fossil or        crease the amount of waste to process.                    Challenges ahead will involve finding pro-
biomass fuel consisting of or containing car-       A recent grant from the USDA Natural                   cesses, uses and markets for these co-prod-
bon is converted to a useable gaseous prod-      Resources Conservation Service (NRCS) is                  ucts. Possibilities may include animal feed,
uct without complete combustion of the           funding assembly and testing of a portable                fertilizers, soil conditioners, construction
fuel. It is a process that occurs in an oxygen   anaerobic digester and gasifier system at                 materials or chemical extraction.
deficient environment at high tempera-           the Biological and Agricultural Engineering                  Dairy manure could be an excellent feed-
tures. The resulting fuel is a gas product       Department at Texas A&M. The idea is to                   stock for alternative energy systems to gen-
called syngas that consists primarily of         use liquid manure to generate methane gas                 erate heat, power or fuel. The heating value
varying ratios of hydrogen and carbon            with the anaerobic digester, and dried sepa-              of dairy manure on a dry ash free basis is
monoxide (CO). Syngas can be further pro-        rated solids from the manure as feedstock                 estimated at 8,500 BTUs per pound, accord-
cessed into other fuels or products by chem-     for the gasifier, to generate energy that                 ing to extensive field research by the Texas
ical conversion, or burned to heat a conven-     could be used to produce electricity for a                AgriLife Research and Texas AgriLife Ex-
tional boiler. It can also replace natural gas   producer’s home, barn or irrigation pump.                 tension. This heating value is comparable
in a gas turbine.                                Energy production from the portable gasifi-               to as-received low grade coal. In addition,
   Opportunities exist for converting ma-        er may be as high as 11 million BTUs per                  the use of dairy manure for alternative fuel
nure to this type of energy on-site or on-       day, or a fuel equivalent of 75 gallons of                could be an excellent mitigation measure to
farm. Small and modular gasification and         diesel or 116 gallons of propane. When com-               reduce excessive nutrient loading of land,
anaerobic digestion units could be installed     pleted, both units will be on skids and could             groundwater and waterways.

Questioning the benefits of biofuels
by Ragan Adams, MS, DVM,                         greenhouse gases into the atmosphere                      worse, just at the time when we need to be
 Colorado State University                       when they are burned and plowed, but also                 bringing down carbon emissions.”
                                                 deprive the planet of natural ecosystems                     Dr. Searchinger’s study shows the pur-
Since the biofuel industry blossomed             that absorb carbon emissions better than                  chase of biofuels in Europe and the U.S.
based upon the hope that plant-based fuel        cropland.                                                 leads indirectly to the destruction of natu-
use can reduce U.S. dependence on foreign           In a conversation with reporter Eliza-                 ral habitats far afield. For instance, if veg-
oil, dairy producers have been plagued by        beth Rosenthal published in the New York
skyrocketing feed costs. However, the rush       Times February 8, Timothy Searchinger,
to support biofuel use as the answer to en-      lead author of one of the studies and a re-                  Among the mounting evidence ques-
ergy independence in the U.S. has come           searcher in environment and economics at                     tioning the benefit of biofuels are two
under substantial question in the past sev-      Princeton University said, “Most of the bio-
eral months.                                     fuel that people are using or planning to
                                                                                                              articles published online in the Febru-
   Plant-based fuels were originally billed      use would probably increase greenhouse                         ary 7, 2008 issue of Science maga-
as better than fossil fuels because the car-     gasses substantially. Previously there’s                       zine, which declare that biofuel use
bon released when they were burned was           been an accounting error: Land use change                      cause more greenhouse gas emis-
balanced by the carbon absorbed when the         has been left out of prior analysis.”
plants grew. Study after study recently             Joseph Fargione, lead author of the sec-
                                                                                                                sions than conventional fuels if the
published question the promotion of biofu-       ond paper and a scientist at the Nature                         full emissions costs of producing
els, regardless of their origin, as the most     Conservancy said, “The clearance of grass-                         them are taken into account.
rational answer.                                 land releases 93 times the amount of green-
   The impact of biofuel use differs depend-     house gas that would be saved by the fuel
ing upon the model used to analyze their         made annually on that land. So for the next               etable oil prices go up globally as they have
benefit. Initially, the concept of making fuel   93 years you’re making climate change                     because of increased demand for biofuel
from plants that are a renewable resource                                                                  crops, more new land is inevitably cleared
seemed sound, but the analysis was sim-           Western Dairy News is published as a service to
                                                                                                           as farmers in developing countries try to
plistic because the process of turning plants     people interested in the health and welfare of the       get in on the profits.
into fuels causes its own emissions.              Western dairy industry. Archives of this publication        Dr. Fargione also said that the dedication
   Among the mounting evidence question-          may be found at:                                         of so much cropland in the U.S. to growing
ing the benefit of biofuels are two articles      http://animalscience-extension.tamu.edu/dairy/wdn.html   corn for bioethanol had caused indirect
published online in the February 7, 2008                                                                   land use changes far away. Previously, Mid-
issue of Science magazine, which declare          For further information contact:                         western farmers had alternated corn with
                                                               Dr. Ragan Adams, Editor
that biofuel use cause more greenhouse gas                           ILM, CSU-VTH                          soy in their fields from one year to the next.
emissions than conventional fuels if the full                    300 W. Drake Road                         Now, many grow only corn – meaning that
emissions costs of producing them are                           Fort Collins, CO 80523                     soy has to be grown elsewhere.
taken into account.                                                  970-297-0371                             In the wake of the new studies, 10 of the
   These studies include in their models the                                                               United States’s most eminent ecologists
global environmental cost of biofuel produc-      Material published in Western Dairy News is not          and environmental biologists recently sent
tion. When crops are used to manufacture          subject to copyright. Permission is therefore grant-     a letter to President Bush and Speaker of
biofuels, more land must be put into crop         ed to reproduce articles, although acknowledge-          the House Nancy Pelosi, urging a reform of
production to meet the additional needs.          ment of the source is requested.                         biofuels policies. “We write to call your at-
The destruction of natural ecosystems –                   Cooperative Extension programs                   tention to recent research indicating that
whether rain forest in the tropics or grass-         are available to all without discrimination.          many anticipated biofuels will actually ex-
lands in South America – not only releases                                                                 acerbate global warming,” said the letter.

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