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Biomass is plant or animal material used as fuel to produce electricity or heat. Examples are wood, energy crops and waste from forests, yards, or farms. More often than not, the word biomass simply denotes the biological raw material the fuel is made of. The word biofuel is usually reserved for liquid or gaseous fuels, used for transportation. The U. Wood and wood residues is the largest biomass energy source today.
Wood can be used as a fuel directly or processed into pellet fuel or other forms of fuels. Other plants can also be used as fuel, for instance cornswitchgrassmiscanthus and bamboo. Sewage sludge is another source of biomass. There is ongoing research involving algae or algae-derived biomass.
Biomass is also used to produce fibers and industrial chemicals. Based on the source of biomass, biofuels are classified broadly into three major categories: [7]. First-generation biofuels are derived from food sources, such as sugarcane and corn starch. Sugars present in this biomass are fermented to produce bioethanolan alcohol fuel which serve as an additive to gasoline, or in a fuel cell to produce electricity.
Proponents argue that there is huge potential for second generation biofuels. Third-generation biofuels refer to those make a photo frame using waste material error from microalgae.
Upgrading raw biomass to higher grade fuels can be achieved by different methods, broadly classified as thermal, chemical, or biochemical. Thermal conversion processes use heat as the dominant mechanism to upgrade biomass into a better and more practical fuel.
The basic alternatives are torrefactionpyrolysisand gasificationthese are separated principally by the extent to which the chemical reactions involved are allowed to proceed mainly controlled by the availability of oxygen and conversion temperature. There are other less common, more experimental or proprietary thermal processes that may offer benefits, such as hydrothermal upgrading. A range of chemical processes may be used to convert biomass into other forms, such as to produce a fuel that is more practical to store, transport and use, or to exploit some property of the process itself.
Many of these processes are based in large part on similar coal-based processes, such as the Fischer-Tropsch synthesis. As make a photo frame using waste material error is a natural material, many highly efficient biochemical make a photo frame using waste material error have developed in nature to break down the molecules of which biomass is make a photo frame using waste material error, and many of these biochemical conversion processes can be harnessed.
In most cases, microorganisms are used to perform the conversion process: anaerobic digestionfermentationand composting. Glycoside hydrolases are the enzymes involved in the degradation of the major fraction of biomass, such as polysaccharides present in starch and lignocellulose. Thermostable variants are gaining increasing roles as catalysts in biorefining applications, since recalcitrant biomass often needs thermal treatment for more efficient degradation. Biomass can be directly converted to electrical energy via electrochemical electrocatalytic oxidation of make a photo frame using waste material error material.
This can be performed directly in a direct carbon fuel cell[14] direct liquid fuel cells such as direct ethanol fuel cella direct methanol fuel cella direct formic acid fuel cella L-ascorbic Acid Fuel Cell vitamin C fuel cell[15] and a microbial fuel cell. IEA defines carbon neutrality and carbon negativity like so: «Carbon neutrality, or 'net zero,' means that any CO 2 released into the atmosphere from human activity is balanced by an equivalent amount being removed.
Becoming carbon negative requires a company, sector or country to remove more CO 2 from the atmosphere than it emits. Likewise, Hanssen et al. When combusted in combustion facilities with the same heat-to-electricity conversion efficiency, oven dry wood emits slightly less CO 2 per unit of heat produced, compared to oven dry coal. Further, raw biomass can have higher moisture content compared to some common coal types. Some research groups e. Chatham House therefore argue that «[ How much «extra» CO 2 make a photo frame using waste material error is released depends on local factors.
Some research groups estimate relatively low extra emissions. Other research groups estimate relatively high make a photo frame using waste material error emissions. The assumed moisture make a photo frame using waste material error for coal is not provided. Is the extra CO 2 from biomass a problem? IPCC argues that focusing on gross emissions misses the point, what counts is the net effect of emissions and absorption taken together: «Estimating gross emissions only, creates a distorted representation of human impacts on the land make a photo frame using waste material error carbon cycle.
While forest harvest for timber and fuelwood and land-use change deforestation contribute to gross emissions, to quantify impacts on the atmosphere, it is necessary to estimate net emissions, that is, the balance of gross make a photo frame using waste material error and gross removals of carbon from the atmosphere through forest regrowth […]. IEA Bioenergy provide a similar argument: «It is incorrect to determine the climate change effect of using biomass for energy by comparing GHG emissions at the point of combustion.
What is sustainable managed forests? In the context of CO 2 mitigation, the key measure regarding sustainability is the size of the forest carbon stock. In a research paper How To Make A Frame Using Cardboard Jump for FAO, Reid Miner writes: «The core objective of all sustainable management programmes in production forests is to achieve a long-term balance between harvesting and regrowth. Is the forest carbon stock stable? Globally, the forest carbon stock has decreased 0. Some research groups seem to want more than «just» sustainably managed forests, they want to realize the forests full carbon storage potential.
For instance EASAC writes: «There is a real danger that present policy over-emphasises the make a photo frame using waste material error of forests in energy production instead of increasing forest stocks for carbon storage.
In addition they argue that there is a loss of soil carbon due to the harvest operations. Research show that old trees absorb more CO 2 than young trees, because of the larger leaf area in full grown trees. The IPCC writes: «When vegetation matures or when vegetation and soil carbon reservoirs reach saturation, the annual removal of CO 2 from the atmosphere declines towards zero, while carbon stocks can be maintained high confidence.
However, accumulated carbon in vegetation and soils is at risk from future loss or sink reversal triggered by disturbances such as flood, drought, fire, or pest outbreaks, or future poor management high confidence. Regarding the net climate effect of conversion from natural to managed forests, the IPCC argues that it can swing both ways: «SFM [sustainable forest management] applied at the landscape scale to existing unmanaged forests can first reduce average forest carbon stocks and make a photo frame using waste material error increase the rate at which CO 2 is removed from the atmosphere, because net ecosystem production of forest stands is highest in intermediate stand ages Make a photo frame using waste material error et al.
The net impact on the atmosphere depends on the magnitude of the reduction in carbon stocks, the fate of the harvested biomass i. Thus, the impacts of SFM on one indicator e. Sustainably managed forest landscapes can have a lower biomass carbon density than unmanaged forest, but the younger forests can have a higher growth rate, and therefore contribute stronger carbon sinks than older forests Trofymow et al. In other words, there is a tradeoff between the benefits of having a maximized forest carbon stock, not absorbing any more carbon, and the benefits of having a portion of that carbon stock «unlocked», and instead working as a renewable fossil fuel replacement tool.
When put to work, this carbon is constantly replacing carbon in fossil fuels used in for instance heat production and baseload electricity production — sectors where it is un-economical or impossible to use intermittent power sources like wind or solar.
Being a renewable carbon source, the unlocked portion keep cycling back and forth between forests and forest products like lumber and wood pellets. For each cycle it replaces more and more of the fossil based alternatives, e. FAO researcher Reid Miner argues that the «competition» between locked-away and unlocked forest carbon is won by the unlocked carbon: «In the long term, using sustainably produced forest biomass as a substitute for carbon-intensive products and fossil fuels provides greater permanent reductions in atmospheric CO 2 than preservation does.
Summing up the above, IEA Bioenergy writes: «As the IPCC has pointed out in several reports, forests managed for producing sawn timber, bioenergy and other wood products can make a greater contribution to climate change mitigation than forests managed for conservation alone, for three reasons. First, the sink strength diminishes as conservation forests approach maturity.
Second, wood products displace GHG-intensive materials and fossil fuels. Third, carbon in forests is vulnerable to loss through natural events such as insect infestations or wildfires, as recently seen in many parts of the world including Australia and California.
Managing forests can help to increase the total amount of carbon sequestered in the forest and wood products carbon pools, reduce the risk of loss of sequestered carbon, and reduce fossil fuel use. The IPCC further suggest that the possibility to make a living out of forestry incentivize sustainable forestry practices: «[…] SFM [sustainable forest management] aimed at providing timber, fibre, biomass and non-timber resources can provide long-term livelihood for communities, reduce the risk of forest conversion to non-forest uses make a photo frame using waste material error, crops, etc.
The National Association of University Forest Resources Programs agrees: «Research demonstrates that demand for wood helps keep land in forest and incentivizes investments in new and more productive forests, all of which have significant carbon benefits. Favero et al. Possibly strengthening the arguments above, data from FAO show that most wood pellets are produced in regions dominated by sustainably managed forests. Carbon stock decreased from Wood pellet production in these areas combined was Some research groups still argue that even if the European and North American forest carbon stock is increasing, it simply takes too long for harvested trees to grow back.
EASAC for instance argues that since the world is on track to pass by the agreed target of 1. They therefore suggest that the EU should adjust its sustainability criteria so that only renewable energy with carbon payback times of less than 10 years is defined as sustainable, [l] for instance wind, solar, biomass from wood residues and tree thinnings that would otherwise be burnt or decompose relatively fast, and biomass from short rotation coppicing SRC.
FutureMetrics argues that it makes no sense for foresters to sell sawlog-quality roundwood to pellet mills, since they get a lot more money for this part of the tree from sawmills. This low-value biomass is mainly sold to pulp mills for paper production, but in some cases also to pellet mills for pellet production. Chatham House further argue that almost all available sawmill residue is already being utilized for pellet production, so there is no room for expansion.
For the bioenergy sector to significantly expand in the future, more of the harvested pulpwood must go to pellet mills. However, the harvest of pulpwood tree thinnings removes the possibility for these trees to grow old and therefore maximize their carbon holding capacity. These are wastes from other forest operations that imply no additional harvesting, and if otherwise burnt as waste or left to rot would release carbon to the atmosphere in any case.
An important presupposition for the «tree regrowth is too slow» argument is the view that carbon accounting should start when trees from particular, harvested forest stands are combusted, and not when the trees in those stands start to grow. When instead assuming that carbon accounting should start when the trees start to grow, it becomes impossible to argue that the emitted carbon constitutes debt.
Prior growth of the forest is irrelevant to the policy question […]. Some researchers limit Make A Photo Frame Using Waste Material Foundation their carbon accounting to particular forest stands, ignoring the carbon absorption that takes place in the rest of the forest. FutureMetrics for instance argue that the whole forest continually absorb CO 2 and therefore immediately compensate for the relatively small amounts of biomass that is combusted in biomass plants from day to day.
IPCC argue along similar lines: «While individual stands in a forest may be either sources or sinks, the forest carbon balance is determined by the sum of the net balance of all stands. When the total is calculated, natural disturbances like fires and insect infestations are subtracted, and what remains is the human influence. This allows for consistency, comparability, and transparency in estimation.
Hanssen et al. But when instead comparing continued pellet production to the more realistic alternative scenarios of 1. The estimate is based on the landscape rather than the individual forest stand carbon accounting practice. Researchers from both sides agree that in the short term, emissions might rise compared to a no-bioenergy scenario.
IPCC for instance states that forest carbon emission avoidance strategies always give a short-term mitigation benefit, but argue that the long-term benefits from sustainable forestry activities are larger: [57].
Relative to a baseline, the largest short-term gains are always achieved through mitigation activities aimed at emission avoidance […]. But once an emission has been avoided, carbon stocks on that forest will merely be maintained or increased slightly.
Similarly, addressing the issue of climate consequences for modern bioenergy in general, IPCC states: «Life-cycle GHG emissions of modern bioenergy alternatives are usually lower than those for fossil fuels […].
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