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Posted on 17-3-13 Another Clean, Green Myth, Biomass Power
Edited from article by Gordon Clark and Mary Booth, Truthout.org, 16 March 2013
Promoted as clean and climate friendly and driven by lucrative renewable
energy subsidies and tax credits, biomass energy - burning wood and other
biological materials to produce heat and power - is on the rise around the
world. However recent scientific and policy developments recognizing that
biomass energy has significant greenhouse gas emissions have blown a major
hole in arguments for treating biomass as a favored renewable energy source
and could fundamentally reshape its future.
Until this past decade an aging biomass industry was composed largely of
industrial boilers, often located at sawmills and paper mills, which burned
manufacturing waste or waste wood to produce industrial heat and power. Some
of these facilities also exported electricity to the grid. In recent years
there has been a surge of interest, borrowing and investment in biomass
power plants in the `industrialised West' often relying on lucrative
renewable energy subsidies and tax credits.
Many of these proposed plants are stand-alone electricity-generating units
uncoupled from a manufacturing facility that plan to produce "renewable"
power for the grid. Critically, most of them plan to burn wood - wood that
is directly sourced from logging operations - rather than waste from paper
mills and other wood-processing facilities. See for example a biomass power
plant proposed for a site on the outskirts of Christchurch which has been
given planning permission by the Dorset County Council Planning Committee.
The $19.4 million plant will burn 25,000 metric tons of wood waste each year
to generate up to 3 megawatts of electricity which will be sold to the NZ
national grid.
Citizens near where these new biomass facilities are proposed often find the
plans alarming. A moderate-sized biomass power plant in the 30-40 megawatt
(MW) range (they can exceed 100 MW) is a huge installation, with a 200 to
300 foot smokestack, a wood chip pile 60 feet tall that can cover several
acres, and an unending stream of tractor-trailers delivering wood fuel.
Cooling towers blow off hundreds of thousands of gallons of water a day as
waste steam, water that is often taken from nearby rivers.
Also to many local residents' surprise, these biomass power plants emit just
as much pollution, and in some cases even more, as coal-fired power plants -
tons of particulate matter, carbon monoxide, nitrogen oxides, volatile
organic compounds, hydrochloric acid, and carcinogens like formaldehyde and
benzene. (1) They also emit carbon dioxide, the primary global warming gas,
and lots of it - far more, it turns out, than fossil fuel plants. Burning
fuels with low energy density and high water content, biomass power plants
are notoriously inefficient and actually emit 40-50% more carbon dioxide per
megawatt hour than coal plants, and more than 300% the carbon dioxide of gas
plants. (2)
How did something that emits so much conventional pollution, and more
greenhouse gases than coal, come to be incentivized as "green" energy?
To some extent, this has been the fault of policymakers who were eager to
advance the cause of renewable energy and failed to critically examine
biomass power. They accepted the two main arguments usually advanced for
biopower's supposedly benign effect on the climate: first, that the carbon
released from burning waste materials such as sawmill trimmings and logging
residues (tree tops and branches) is no greater than the carbon released if
those materials are left to decompose; and second, that biomass fuels such
as switchgrass and trees can be grown and harvested in such a way that each
new crop would absorb or "resequester" equivalent carbon as was released by
the burning of the previous crop. In either case, there is supposedly no net
increase in carbon dioxide emissions - or so the theory goes - and biomass
is therefore as "carbon neutral" and "green" in many policymakers' minds as
wind or solar.
There is a major and obvious flaw in each of these propositions. The problem
with the burning-is-the-same-as-decomposition argument is that burning takes
minutes, while decomposition takes years. (Moreover, decomposition of
logging residues helps build long-lived soil carbon stocks for healthy
forests.) The problem with the "just wait and it will regrow" argument is
even more blatant. Switchgrass crops may indeed be regrown swiftly after
harvest but there are virtually no biomass facilities using switchgrass or
other energy crops as fuel due to prohibitive costs and logistics. Most
existing and proposed biomass plants burn wood but while it takes mere
moments to cut and burn a tree it takes decades to regrow a new one in its
place. This fact is widely recognized when we bemoan the role forest loss
plays in driving global warming, yet it goes curiously unnoted in the
promotion of wood fuels - indeed the exact opposite is assumed and burning
wood magically becomes "carbon neutral."
Perhaps because of growing public concern over the state of our forests,
energy companies and the biomass industry have hastened to portray the newly
emerging fleet of biomass plants as using mostly logging residues and other
waste wood for fuel, attempting to keep greenhouse gas impacts more squarely
in the "it would decompose anyway" zone. However this argument collapses the
moment one reads the permit for one of these plants.
Utility-scale biomass energy plants consume huge amounts of wood - about
12,500 green tons per megawatt per year. The air permit for the 75 MW
Laidlaw biomass plant in Berlin, New Hampshire, USA for instance states the
facility will burn 113 tons of "whole logs" an hour - nearly a million tons
a year or the equivalent of clear-cutting more than an acre of forest every
hour. Such prodigious demand far outstrips available logging residues in
most regions, meaning that each new facility requires cutting hundreds of
thousands, if not millions, of trees each year - trees that would otherwise
continue growing and sequestering carbon dioxide out of the atmosphere.
The good news for the planet is that the renewable energy policies rewarding
such polluting, forest-threatening power plants were written a number of
years ago, and in the interim, as local activists have fought individual
plants, the science of carbon accounting for biomass has taken big leaps
forward. The results have not been good for the industry.
Given its extensive forest cover and centuries-old tradition of burning
wood, New England has been a hotbed of biomass energy development - as well
as citizen opposition to it - so it's not surprising that Massachusetts USA
became the first to do some actual scientific analysis of the issue. To make
sure the state could meet the greenhouse gas reduction goals set in its 2008
Global Warming Solutions Act, Governor Deval Patrick's administration
commissioned the well-regarded Manomet Center to study the carbon impacts of
biomass energy. The primary finding was that when biomass plants burn a
combination of logging residues and whole trees, the net emissions of carbon
dioxide, the primary global warming gas, exceed emissions from an
equivalent-sized coal-fired plant for more than 45 years, and exceed
emissions from an equivalent gas-fired plant for more than 90 years - even
when taking forest regrowth into account.
This central finding was reinforced by a similar study conducted in the
Southeast, which examined biomass fuel sourced from fast-growing pine
plantations and concluded, "the expanded biomass scenario creates a carbon
debt that takes 35-50 years to recover."
The findings of both this study and the Manomet study carry extra weight
given that each had a co-author from the Biomass Energy Resource Center, a
group dedicated to promoting small-scale biomass energy installations.
The scientific reality revealed by these two studies, and a number of others
that have emerged in the past two years, is that when it comes to biomass
power's relative contribution to global warming, the treatment of biomass as
"carbon neutral" couldn't be further from the truth. Industry claims
notwithstanding, there is no quicker way to move carbon into the atmosphere
- the opposite of what we want - than through utility-scale biomass energy
plants that burn millions of trees per year.
In response to the Manomet Study, Massachusetts dramatically reduced its
subsidies to biomass power, finalizing the regulations in August 2012. The
state's Department of Energy Resources' new policy is the first in the
nation to acknowledge that utility-scale biomass plants emit massive amounts
of carbon dioxide, and thus should not be subsidized as renewable energy to
meet the state's greenhouse gas reduction goals. Recognizing that
electricity-only biomass plants are only about 24% efficient, less even than
the 33% efficiency of old line coal-fired plants, the new regulations
require biomass power plants to be at least 50% efficient before receiving
half a renewable energy credit (REC) per megawatt hour, and 60% efficient to
receive a full credit. This standard for the RECs, which are worth millions
of dollars to a utility-scale plant, can only be met by smaller facilities
that utilize waste heat for thermal energy in addition to generating
electricity.
The new Massachusetts regulations had an almost immediate impact on the
industry in the USA. The Russell Biomass project in Russell, Massachusetts,
a 50-megawatt wood-burning power plant under development since 2005, was
abruptly cancelled less than two months after the new rules were announced.
The Russell project was Exhibit A for the type of tree-burners designed to
produce electricity for the grid, with a section in the plant's air permit
stating that it would burn 250,000-350,000 tons of whole tree fuel per year,
along with municipal wood fuel, stump grindings, and pallet grindings.
"Under the final DOER regulations, the project is not technically and
economically viable because of the required 50-percent efficiency, coupled
with the new forest biomass fuel supply limitations,"
said Russell Biomass partner John Bos. "We are unable to modify the plant
design as permitted."
The new Massachusetts regulations could provide a template for other states
and countries that are serious about reducing emissions from the power
sector. High efficiency is one commonsense standard that most people can
agree on for renewable energy, and simply requiring that plants meet a
stringent efficiency standard in order to qualify for renewable energy
credits would do much to reduce the stampede of biomass power development
now underway.
The term `clean and green' when used by business and politicians is now
nothing short of propaganda.
(1) Pollution emission rates are expressed as pounds of pollution per
million Btu of boiler capacity (lb/MMbtu). EPA's "clearinghouse" for air
permits (at http://cfpub.epa.gov/RBLC/) contains data on emissions limits
for the lowest-emitting facilities. The clearinghouse data show overlap in
the permitted emission rates for coal- and biomass-burning facilities for
each pollutant, with the exception of sulfur dioxide, which is usually
emitted at a higher rate by coal plants (although biomass plants burning
construction debris that contains gypsum wallboard residues can have
relatively high sulfur emission rates). The range of rates at the five
lowest-emitting coal facilities and the five lowest-emitting biomass
facilities in the clearinghouse with boilers 100 MMbtu/hr and greater are as
follows:
Filterable PM10 Coal: 0.01 to 0.12 lb/MMBtu; Biomass: 0.0125 to 0.025
lb/ MMBtu Nitrogen oxides (NOx) Coal: 0.067 to 0.07 lb/ MMBtu; Biomass:
0.065 to 0.15 lb/ MMBtu Carbon monoxide (CO) Coal: 0.02 to 0.135 lb/
MMBtu; Biomass: 0.1 to 0.33 lb/ MMBtu Emissions of hazardous air pollutants
(HAPs) including heavy metals, hydrochloric acid, and organic contaminants
including benzene and formaldehyde are estimated using EPA emissions factors
for biomass combustion
(http://www.epa.gov/ttnchie1/ap42/ch01/final/c01s06.pdf), with totals that
range from 10 to more than 40 tons of HAPs per facility.
(2) Biomass has a lower energy content per unit carbon than fossil fuels,
emitting around 213 pounds of CO2 per MMBtu heat content, in contrast to
coal (~206 lb CO2/MMBtu) and natural gas (~117 lb CO2/MMBtu;
http://www.eia.gov/electricity/annual/html/epa_a_03.html). Besides its
relatively low energy content, biomass tends to have high moisture content,
about 45 percent by weight for green wood chips. Energy is required to drive
off that moisture before useful heat can be generated for the boiler, which
further degrades facility efficiency. Our review of multiple biomass permit
applications reveals that peak efficiency of biomass power plants is around
24%, whereas a coal plant is around 34% efficient and a gas plant using
combined cycle technology can be around 45% efficient
efficiency calculated from data in Table 8.2). The combined effect of these
factors is that a biomass plant emits about 3,029 lb CO2 per megawatt-hour
(MWh), versus a typical coal plant (2,086 lb CO2/MWh), or a combined cycle
natural gas plant (883 lb CO2/MWh).
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