April 23, 2014

Biomass Fuel: Worse for Climate than Coal?

A worker unloads a truckload of biomass at the University of British Columbia energy plant.

Paul Joseph Brown/ecosystemphoto.com

A worker unloads a truckload of biomass at the University of British Columbia energy plant.

The crackling log fire, flickering in an open hearth, may win the day for romance or Christmas cards. From the modern viewpoint of efficiency and good health, it’s more of a horror show. Our ancestors, living in unvented huts lit and warmed by open fires, wheezed and coughed their way to early deaths. Burning wood still releases an old-timey scented bouquet of toxins: nitrogen oxides, sulfur dioxides, carbon monoxide, volatile organic compounds, dioxin, and a couple dozen other chemicals classified as hazardous air pollutants, along with ultrafine particles of super-toxic soot that go deep into the lungs. As a 2007 Health Canada review put it, “Even though wood smoke is natural, it is not benign.”

For that reason, a well-run modern biomass-burning power plant is much less smoky than a fireplace. High-tech smoke scrubbers with multisyllabic names like "electrostatic precipitator" and "regenerative thermal oxidizers" scrub their exhaust, and operators work continually to bring down pollution levels, tweaking temperatures and fuels. The state-of-the-art may be UBC’s $34-million Bioenergy Research and Demonstration Facility reported on in the first installment in this series: what comes out of its smokestack is even cleaner than emissions from most natural-gas plants.

Editor's Note
As the world searches for alternatives to climate-altering fossil fuels, the prospect of "grow-your-own" clean energy from plants — so-called biomass fuel — is tantalizing.But this joint Tyee/InvestigateWest investigation reveals that once you clear away the smoke, there are real problems with the carbon-neutral claims being made for this "green" energy.

Read more about the project here.

That achievement is likely exceptional. In the U.S., a Wall Street Journal review of 107 biomass-fueled power plants found that 79 per cent had been cited in the previous five years for violating air or water-pollution standards. Prompted by health concerns, the American Lung Association, Massachusetts Medical Society, and Florida Medical Association have all come out against large-scale wood-burning to produce energy.

Technology, as the UBC facility shows, can keep harmful wood smoke out of the air. But there’s a much bigger question hanging over the wildfire popularity of capturing energy from British Columbia’s forests. As reported yesterday, for all its accomplishments in keeping the air clear, UBC’s high-tech burner nonetheless still emits about 5,000 tons of climate-changing  CO2 a year -- about the same amount as the natural-gas power it replaces.

So, how can UBC claim that the new facility has reduced its emissions by that amount?

The answer to that question holds both the promise and the temptation of burning plant matter -- biomass, whether it comes from trees or straw -- for energy. The promise is that plants grow, capturing carbon from the atmosphere as they do. That means that when we burn one tree, releasing its carbon, the tree that replaces it will capture that carbon again: a fuel that cleans up after itself!

But all that takes time: the clean-up of the carbon released by burning the tree may take decades. Meanwhile, the temptation arises to consider biomass energy "zero-carbon" from the day it’s trucked out of the forest.

British Columbia has put energy from wood at the heart of its Bioenergy Strategy, aimed at reducing the province’s greenhouse gas emissions by a third by 2020, and 80 per cent by 2050. In Europe, former coal power plants are being converted to burn woody biomass instead, allowing several countries to claim to be meeting their targets for emission cuts under Kyoto Protocol rules that consider all biomass energy as zero-carbon today. Selling B.C. wood in pellet form to many of those plants has turned the province into a major exporter of biomass energy.

In reality, however, wood combustion produces unavoidable quantities of climate-changing CO2. And while some or all of that may be taken up into trees that grow in the future, “anything that comes out of a smokestack is still going to have an impact,” notes Ananda Tan, the Vancouver-based Canada/U.S. regional coordinator for the Global Alliance for Incinerator Alternatives.

So has UBC really cut its emissions by 5,000 tons, or not? And what about all those European countries?

Three key dynamics

Three dynamics affect the answer. One is the difference in the energy density -- the amount of energy produced from a given amount of fuel -- between wood and fossil fuels like coal or oil. Another is whether new trees do in fact recapture the carbon released by burning previously harvested trees -- and, crucially, how quickly.

A third is particularly relevant to British Columbia, where 45 million acres of forests have been infested so far by the mountain pine beetle -- and the felling of those trees has doubled in the last few years. The common wisdom is that those trees are going to die, disintegrate and release their carbon anyway, so why not burn them and get some juice for the grid out of them instead? But is that assumption right?

Let’s start with the density problem. Burning a kilogram of coal produces more energy than burning a kilo of wood. Which means that you need to burn more wood to get the same amount of electricity as you would from a smaller amount of ancient carbon in the form of coal or oil, releasing more actual carbon to the atmosphere than if you used the fossil fuel.

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The Intergovernmental Panel on Climate Change confirmed the inference in a 2006 document that evaluated CO2 releases compared to energy produced for 53 different fuels. It determined that wood and wood wastes had a greenhouse emission factor roughly 20 per cent higher than coal. Even after biomass is “densified” in pellets, the U.S. Department of Energy’s Biomass Energy Data Book, determined, “the bulk density (and hence energy density) of most biomass feedstocks is... between about 10 and 40 per cent of the bulk density of most fossil fuels.”

As a result, according to one study by the Manomet Center for Conservation Studies for the Massachusetts Department of Environmental Conservation, burning wood to produce electricity produces 46 per cent more emissions, kilowatt-hour-for-kilowatt-hour, than burning coal. Yes! Burning coal actually produces fewer climate-altering emissions than burning wood.

This startling fact was confirmed again this month, when the Pelham, Mass., based Partnership for Policy Integrity and American Lung Association analyzed 88 biomass power plants in more than two-dozen U.S. states from California to Maine, and reported that on average they emitted 50 per cent more greenhouse gasses per kilowatt of electricity generated than coal plants did. (They also released eight times as much other air pollution as the cleanest fossil fuel, natural gas.)

There are other factors. Wood has to be dried before it can be burned. How’s that done? By burning more wood to heat improbably large dryers. “Think of your clothes drier at home multiplied by about a thousand times,” says Gordon Murray, executive director of the Revelstoke-based Wood Pellet Association of Canada. Then, wood is bulky. It takes more energy, and emissions, to deliver pellets than coal to generate a needed amount of power.

But if new growing trees are recapturing all the carbon expended in harvesting, drying, shipping and burning woody biomass, the volume that’s being cut, shipped and burned shouldn’t make a difference, right? It’s all net-carbon-zero in the end.

Are new trees cleaning up after old?

That gets us to the second question: will growing new trees actually recapture the carbon released when the last generation was burned? Researchers who monitored carbon emissions from forests regenerating on Vancouver Island, found that three years after being logged, a hectare of regenerating Douglas Fir seedlings, far from capturing carbon, was releasing 22 tons of it over a year. Even 18 years after being logged, another area was still releasing 5 tons of CO2 per hectare.

That’s assuming new forests are planted. The carbon “offset” certificates that many companies buy to cancel out their fossil-fuel emissions by capturing an equivalent amount of carbon in a growing forest typically meet detailed standards to ensure that the carbon is really being removed from the atmosphere.

The same careful accounting doesn’t apply to biomass destined for fuel: British Columbia has struggled historically to ensure that Crown forests are replanted once their trees are cut down, much less that they actually balance out carbon-wise. The number of natural resource officers on the provincial payroll tumbled by 46 per cent between 2009 and 2012, with actual inspections of forestry operations falling by two-thirds. In 2012, British Columbia’s auditor-general found that provincial ministries were failing to ensure that reforestation kept up a sustainable pace with timber harvesting.

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Lastly, there are all those trees dead and dying from the beetle plague. They’re marked to supply nearly half the additional renewable electricity produced under B.C.’s Bioenergy Strategy through 2020. And after all, they’re just going to decompose and release their carbon anyway, so why not?

Because, says David Moore of the University of Arizona, dead forests don’t actually give up all that much carbon, at least right away. Moore tracked CO2 coming off of forests in Colorado for 10 years after they were hit by beetles. “We didn’t see a big release,” Moore said. “Over this 10-year period, [carbon]’s not going anywhere. It’s just staying there.”

It’s not only that standing trees hold a lot of carbon still tied up in their trunks and branches. It’s also that once the trees die they stop hosting the billions of underground fungi and microbes that suckled on the living trees’ roots, and exhaled carbon dioxide. Dead trees equal fewer fungi and microbes, equals less CO2 being exhaled. Once trees do fall over, some of the carbon released as they decay gets absorbed into the soil, rather than into the air.

Of course, standing dead trees are also potential fuel for forest fires, which release their carbon as certainly as if they were burned as fuel, only without any benefit to the economy.

Seeking the carbon-neutral point

Still, if enough young trees are planted when we burn today’s biomass harvest, then at some point several decades out, the carbon released from burning that wood will have been recaptured in trees. At that point, if tree-growing and burning are in perfect balance, the climate effect of using wood for fuel will indeed be neutral.

But we’re a long way from that today, with no guarantee we’ll ever reach a balance of burning and growing. Doing all the sums to calculate the point when today’s carbon emissions from biomass will have been recaptured is a daunting task.

The Manomet Center’s study for the state of Massachusetts tried. It calculated, based on in-state data, that even a switch from coal to biomass fuel in power generation today would still take at least 20 years and probably more like 50 before moving into the positive column for the climate by becoming truly carbon neutral. If wood were chosen in place of natural gas to substitute for coal, the climate break-even point doesn’t come until the 22nd century.

Other research, reported in the latest IPCC climate impacts report, suggests the same goes for Europe. Continental claims of reduced emissions from conversion to biomass energy will be “offset partly or entirely for decades or centuries,” the report said, because of increased carbon releases from logged-over land.

The forest or the trees

That conclusion sparks vigorous rebuttal from Michael Weedon, executive director of the BC Bioenergy Network, an industry group supported primarily by provincial and other government grants. “That’s a seriously flawed report,” Weedon says. Mainly, he adds, Manomet’s assumption that whole trees would be cut to generate electricity overlooked mill residues -- the source of more than half of B.C.’s anticipated biomass energy.

European and North American trade groups have taken up the same chorus, sponsoring a report contesting Manomet’s findings on similar grounds. Eighty-five per cent of B.C. fuel biomass, that report added, comes from sawmill waste, with the rest coming from logs judged unsuitable for lumber.

The proportion of harvested wood that’s classified as unsuitable for lumber and therefore eligible to become biomass fuel -- 15 to 20 per cent of what’s cut, according to industry estimates -- has been a contested issue in British Columbia’s forests in the past. It may become contentious again, if the findings of researcher Caren Dymond are factored into decisions about whether to burn those “unsuitable” trees for energy.

Dymond, a staff scientist with the B.C. Ministry of Forests, worked on the first comprehensive study to break down the “carbon budget” of B.C.’s biomass energy industry. She looked specifically at whether cutting down beetle-infested trees for power makes sense for the climate.

Her finding: if 85 per cent or more of the trees in a forest are fatally infested and dead or dying, it’s better for the climate to clear them out for fuel and replant new saplings that will suck up carbon. But if as few as one tree in five in a forest stand will survive the beetles, cutting it for fuel is a net minus for the climate. Even if the wood replaces dirty coal in power production, more carbon will be retained by leaving the dead trees standing than by burning their biomass.

UBC’s climate claims for its new power plant may nonetheless have some validity. Although the plant releases about as much greenhouse gas as the one whose energy production it supplants, much of the biomass it burns is urban wood waste. In the past, that might have been sent to the landfill where, decomposing beneath tons of other trash in the absence of oxygen, it would have released methane, a greenhouse gas 21 times more potent than CO2. (Nowadays, though, landfills almost uniformly neutralize the methane; some even produce power from it.)

But the UBC plant is far from typical. Worldwide, a huge amount of biomass energy is obtained from wood not by converting it to syngas but rather the old-fashioned way: simply by burning the stuff. “Bioenergy from biomass is not carbon neutral,” Dymond said. “And the emissions need to be calculated and accounted for over time.”

That raises some big questions about whether B.C.’s ability to supply the world with growing volumes of biomass from climate-friendly energy forests an live up to its promise.

Those questions will be tackled in the final part of this series, running tomorrow on The Tyee.


Read the previous article in this series: "Are Climate Claims for Burning Renewable Trees a Smokescreen?"

Read the next article in this series: "Sketchy Claims Inflate B.C.'s Wood Energy Exports"


15 Key Dates in the Wood Burning Movement

View the full timeline.

Olivia Henry contributed to this report, which was supported by the Fund of Investigative Journalism and a Tyee Fellowship for Investigative Reporting. The Tyee award is funded by Tyee readers to pursue a major journalism project in the public interest for British Columbians.

2 thoughts on “Biomass Fuel: Worse for Climate than Coal?

  1. Carbon release is not the main problem . Mercury release is ! How good are the new furnaces at removing Mercury and the other heavy metals that have been
    extracted from the atmosphere over their growing period . Even if they do extract all what happens to mercury ? Sell it in ever greater quantities to the new breed of
    gold miners who extract gold from ore by making Amalgam & then evaporating mercury back to the atmosphere . Burning vast amounts of gas in the process that also releases Mercury . Just cutting down the trees using chain saws adds to the Mercury . Getting the wood out of the forest to the power plant burns more oil
    produces more mercury . More tyres are used . More mercury as oil is converted to rubber . Rubber crumb is not as Green as you think once crumbed the surface area is greatly increased so the rubber now releases even more mercury into the run off water and atmosphere on and above the roads .
    Even the tarmac on roads contains oil and slowly releases mercury . Old mercury mines and Gold workings are releasing mercury to the atmosphere and
    environment years after they were in operation . Oil shale releases even more mercury than oil . Aviation fuel ,trucking adds to the burden .

    If you are going to investigate go deeper . Towns old and new are nothing more than recycling plants for mercury .

    Airports , large car parks (Hence large Hospitals shopping malls , train & bus stations ) , rivers carrying water from mine workings to reservoirs used for drinking
    and irrigation cycle vast quantities of mercury through us and our autistic children via contaminated fields cattle & fish .

    The answer more trees in towns trapping air born mercury in wood . More forests dedicated to become ancient forests , not for recycling mercury at an
    ever increasing rate but locking it up for ever or at least to a time when we can have complete mercury extraction .

    Mercury causes genetic change in all living organisms and is partially responsible for Evolution . Plants will evolve , some will take in less Mercury , Zinc etc but others will evolve to take in more . We can possibly use the problem to dig ourselves out . We have to encourage nature to find a way out . Laboratory stressing the plants with the levels of mercury we can expect to see in 10 years time at current rate of increase . Looking for changed varieties & selecting what we want . Plants with less mercury burden for food crops and varieties that trap more mercury for filters . The mercury burden slows down plant growth , child development in the womb . It may be too late unless we take quick action to remedy the situation .

    I always wondered why the dung beetle was so revered in Ancient Egypt but I think it quite possible they went the same way as we are going .
    Good farming is a mixture of crops & animal . Animals eat the stubble converting it to dung the dung beetle buries the dung and fertilises the ground .
    To be a very good farmer you rotate the crop because different crops extract different minerals from the atmosphere ,

    Eating a variety of foods is not just good for us but good for the soil.

    Mercury has been used from ancient times in Egypt , India , Tibet , China .The Hindu god Shiva has been around a long time . Mercury is referred to as
    ‘The seed (sperm) of Shiva’ the god of destruction & renewal . Sounds like a description of Evolution to me .

    Mercury through genetic damage can cause death or new life to be created , not in the same form but life that may have a better chance of surviving than that
    from whence it came . Ring any bells ? replace ‘ Mercury through genetic damage’ by GOD (Gold Ordained Damage)

    !!Suggestion !!
    Trials of Maize where seed are subject to various concentrations mercury vapour for various lengths of time .

    We have inadvertently done this for thousands of years by using mercury compounds to kill pest , mold etc but we should actively look for induced new strains that either soak up more heavy metals/C,S,P,N or less from air . !!!!!! Using a standardised soil !!!!!!!

    All our serial crops , fast growing trees should be tested for take up of elements . GM crops have been with us from the dawn of time .

    Bob Huggins Teacher of Math , Physics , Chemistry , Biology , Electronics , Computing

    Just to change topic !
    One way of getting rid of guns ! Make bullets of Prada rather than lead . Evolution will very quickly take care of the problem !

    Sorry about end .My wife teaches Religion , Philosophy ,Italian , French , German so I have to bring in GODS but to me all religions go back to the worship of
    Mercury as the giver of gold . Three in one , Solid , Liquid , Vapour forms of Mercury . Holy ghost = mercury vapour ! 9000 BC or more !

    If you want a title , ‘ The road to Mercury ‘ it was once called the Silk Road ( Flowing mercury looks much like silk )

  2. Yes, it does take more wood than coal or gas to generate the same electricity, so immediate carbon releases are greater. But residence time in the atmosphere of biogenic carbon is decades or around a century. Fossil carbon is a new entry into the biosphere. It is taken up in plants, in the ocean chemically causing acidification, and in rocks. While 2/3rds will be gone in a century, it will take up to 125,000 years or more to absorb it all.

    James Hansen’s new piece – a must read on the order of Target CO2 – http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0081648 – notes: “We bookkeep fossil fuel and deforestation carbon separately, because the larger fossil fuel term is known more accurately and this carbon stays in the climate system for hundreds of thousands of years. Thus fossil fuel carbon is the crucial human input that must be limited. Deforestation carbon is more uncertain and potentially can be offset on the century time scale by storage in the biosphere, including the soil, via reforestation and improved agricultural and forestry practices.”

    The bioenergy critics miss this point. They mush the two carbon sources together. But when it is critical to reduce CO2 now, there is a point to use bioenergy where there are no other feasible options, because biogenic carbon will have heat-trapping effects like fossil CO2 while it’s up there. So general use for electrical generation is questionable when solar,wind and storage are becoming real options.

    Where biomass for energy is most needed is liquid fuels, and that for larger vehicles that cannot fully employ electricity – jet airplanes, ships, trucks and non-electrified rail. It is challenging enough to gain sufficient biomass to meet these needs in an environmentally and economically sustainable matter, without having a whole lot be diverted to power plants that have other options.

    Science backs up the point that bug-kill trees and other fire-endangered stands will lose only about 15% of their carbon in fires. So cutting down forests to avoid fires and use the biomass for energy indeed has a much higher carbon profile. Better to let nature take its course, unless other goals are priority for thinning operations such as preserving forest and wildlife species. Forest slash is a potential feedstock that is now burned or allowed to decay into the atmosphere. Dedicated energy crop trees such as poplar or willow might also serve as feedstock, as long as the land use considerations are taken into account.