Biomass

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For the use of the term in ecology, see Biomass (ecology).

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Simple use of biomass fuel (Combustion of wood for heat).

Renewable energy
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Biofuels Biomass Geothermal Hydro power Solar power Tidal power Wave power Wind power

Biomass refers to living and recently dead biological material that can be used as fuel or for industrial production. Most commonly, biomass refers to plant matter grown for use as biofuel, but it also includes plant or animal matter used for production of fibres, chemicals or heat. Biomass may also include biodegradable wastes that can be burnt as fuel. It excludes organic material which has been transformed by geological processes into substances such as coal or petroleum.

Biomass is grown from several plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sugarcane ^[1] and oil palm (palm oil). The particular plant used is usually not very important to the end products, but it does affect the processing of the raw material. Production of biomass is a growing industry as interest in sustainable fuel sources is growing.^{[citation needed]}

Although fossil fuels have their origin in ancient biomass, they are not considered biomass by the generally accepted definition because they contain carbon that has been "out" of the carbon cycle for a very long time. Their combustion therefore disturbs the carbon dioxide content in the atmosphere.

Plastics from biomass, like some recently developed to dissolve in seawater, are made the same way as petroleum-based plastics, are actually cheaper to manufacture and meet or exceed most performance standards. But they lack the same water resistance or longevity as conventional plastics.^[2]

1 Processing and uses
2 Environmental impact
3 Biomass production for human use and consumption
4 See also
5 References
6 External links

Processing and uses

Biomass which is not simply burned as fuel may be processed in other ways such as corn.

Low tech processes include:^[3]

composting (to make soil conditioners and fertilisers)
anaerobic digestion (decaying biomass to produce methane gas and sludge as a fertiliser)
fermentation and distillation (both produce ethyl alcohol)

More high-tech processes are:

Pyrolysis (heating organic wastes in the absence of air to produce gas and char. Both are combustable.)
Hydrogasification (produces methane and ethane)
Hydrogenation (converts biomass to oil using carbon monoxide and steam under high pressures and temperatures)
Destructive distillation (produces methyl alcohol from high cellulose organic wastes).
Acid hydrolysis (treatment of wood wastes to produce sugars, which can be distilled)

Burning biomass, or the fuel products produced from it, may be used for heat or electricity production.

Other uses of biomass, besides fuel and compost include:

Building materials
Biodegradable plastics and paper (using cellulose fibres)

Environmental impact

Biomass is part of the carbon cycle. Carbon from the atmosphere is converted into biological matter by photosynthesis. On death or combustion the carbon goes back into the atmosphere as soil. This happens over a relatively short timescale and plant matter used as a fuel can be constantly replaced by planting for new growth. Therefore a reasonably stable level of atmospheric carbon results from its use as a fuel. It is commonly accepted that the amount of carbon stored in dry wood is approximately 50% by weight.^[4]

Though biomass is a renewable fuel, and is sometimes called a "carbon neutral" fuel, its use can still contribute to global warming. This happens when the natural carbon equilibrium is disturbed; for example by deforestation or urbanization of green sites. When biomass is used as a fuel, as a replacement for fossil fuels, it still puts the same amount of CO₂ into the atmosphere, and is not a solution to global warming.^[5]^[6]^[7]

Despite harvesting, biomass crops may sequester (trap) carbon. So for example soil organic carbon has been observed to be greater in switchgrass stands than in cultivated cropland soil, especially at depths below 12 inches.^[8] The grass sequesters the carbon in its increased root biomass. But the perennial grass may need to be allowed to grow for several years before increases are measurable.^[9]

Biomass production for human use and consumption

BIOME ECOSYSTEM TYPE	Area	Mean Net Primary Production	World Primary Production	Mean biomass	World biomass	Minimum replacement rate
	(million km²)	(gram dryC/sq metre/year)	(billion tonnes/year)	(kg dryC/sq metre)	(billion tonnes)	(years)
Tropical rain forest	17.0	2,200	37.40	45.00	765.00	20.50
Tropical monsoon forest	7.5	1,600	12.00	35.00	262.50	21.88
Temperate evergreen forest	5.0	1,320	6.60	35.00	175.00	26.52
Temperate deciduous forest	7.0	1,200	8.40	30.00	210.00	25.00
Boreal forest	12.0	800	9.60	20.00	240.00	25.00
Mediterranean open forest	2.8	750	2.10	18.00	50.40	24.00
Desert and semidesert scrub	18.0	90	1.62	0.70	12.60	7.78
Extreme desert, rock, sand or ice sheets	24.0	3	0.07	0.02	0.48	6.67
Cultivated land	14.0	650	9.10	1.00	14.00	1.54
Swamp and marsh	2.0	2,000	4.00	15.00	30.00	7.50
Lakes and streams	2.0	250	0.50	0.02	0.04	0.08
Total continental	149.00	774.51	115.40	12.57	1,873.42	16.23
Open ocean	332.00	125.00	41.50	0.003	1.00	0.02
Upwelling zones	0.40	500.00	0.20	0.020	0.01	0.04
Continental shelf	26.60	360.00	9.58	0.010	0.27	0.03
Algal beds and reefs	0.60	2,500.00	1.50	2.000	1.20	0.80
Estuaries & mangroves	1.40	1,500.00	2.10	1.000	1.40	0.67
Total marine	361.00	152.01	54.88	0.01	3.87	0.07
Grand total	510.00	333.87	170.28	3.68	1,877.29	11.02

Source: Whittaker, R. H.; Likens, G. E. (1975). "The Biosphere and Man", in Leith, H. & Whittaker, R. H.: Primary Productivity of the Biosphere. Springer-Verlag, 305-328. ISBN 0-3870-7083-4. ; Ecological Studies Vol 14 (Berlin)