Biomass

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82% of the biomass of plant origin and the highest productivity in the humid tropical forests reached
Sugar cane is an important supplier of biomass, which is used as food or for energy

As biomass the mass of will creatures or their body parts called. These substance mixtures are quantified using their mass .

In ecology , biomass is often only recorded for selected, spatially clearly defined ecosystems or only for specific, individual populations . Occasionally there are also attempts to estimate the biomass of the entire ecosphere .

There is no uniform term biomass in ecology. In energy technology , biomass only refers to biomass that can be used for energy purposes.

term

So far no uniform biomass term could be established. The biomass terms that can be found in the literature differ to a greater or lesser extent. They can also be divided into two groups:

  • Ecological biomass terms are not uniform. One reason is that biomass changes while living things interact with each other and with their inanimate environment. There is currently no agreement on the definition. Instead, a colorful variety of ecological biomass terms exist side by side.
  • Energy-technical biomass terms exclusively include those biotic substances that can be used as energy sources . The various energy-related biomass terms differ from one another only in nuances.

Ecological term "biomass"

The development of the ecological term biomass leads back to the 1920s. At that time, the Russian natural scientist Vladimir Ivanovich Wernadski (1863–1945) tried to estimate the mass of all earthly living things taken together. He first presented his estimates in 1922 or 1923 when he was lecturing on geochemistry in Paris . An essay accompanying the lecture was published in French in 1924. After further deliberation, Vernadski had a short book in Russian follow in 1926. In his considerations, however, he did not yet use the term biomass .

The term biomass was introduced a year later. It was introduced by the German zoologist Reinhard Demoll (1882–1960). The name was picked up in 1931 by the Russian oceanographer Lev Aleksandrovich Zenkevich (1889–1970):

"By biomass (Demoll) we term the quantity of substance in living organisms per unit of surface or volume."

"With biomass ([according to Reinhard] Demoll) we denote the amount of substance in living organisms per unit of surface area or [per unit] of volume."

- Lev Aleksandrovich Zenkevich : Fish-food in the Barents Sea. (Introduction). In: LA Zenkevich, VA Brotsky, A. Dektereva: Fish-food of the Barents Sea. In: Reports of State Oceanographical Institute Moscow, Session I. 4 (1931)

Zenkevich - and before him Demoll - simply called biomass the mass that all living organisms in a certain area have taken together. This shows the first definition of the ecological biomass term, which is still used.

  • Biomass (Demoll 1927): mass of living beings per area.

Zenkevich influenced the first scientific publication that had the term biomass in its title . It was also written by a Russian. In 1934, the aquatic biologist Veniamin Grigor'evič Bogorov (1904–1971) published his study Seasonal Changes in Biomass of Calanus finmarchicus in the Plymouth Area in 1930 .

Bogorov studied the biomass of all copepods of the species Calanus finmarchicus in the waters of Plymouth . Accordingly, he considered the biomass of a certain population - that is, the individuals of a species within a certain area , which together form a reproductive community. Bogorov's study also shows that he only measured the biomass after the captured organisms had been dried over calcium chloride in a desiccator. So he measured her dry weight. Thus Bogorov developed a second definition of the ecological biomass term, which is also valid to this day.

  • Biomass (Bogorov 1934): Common dry mass of all individuals in a population.

Two different definitions of the ecological term biomass had already been developed within seven years. In the decades that followed, many more were added that deviated more or less strongly from the two original definitions:

  • Most ecological biomass terms refer to dried biomass. Occasionally, however, the water content is not calculated.
  • Some ecological biomass terms include both living and dead biomass. Others relate solely to living biomass.
  • Most ecological biomass terms include the mass of cells. And they also include things that are secreted or secreted by cells. Occasionally, however, only the cell substance is referred to as biomass.
  • In the past, many ecological biomass terms only referred to the masses of plants and animals. The mass of the microorganisms is also increasingly taken into account.

No ecological biomass term includes fossil fuels , kerogen or biogenic sedimentary rocks . Although those substances are modified forms of dead biomass.

Energy-technical biomass term

The energy-technical biomass term exclusively includes animal and vegetable products that can be used to generate heating energy , electrical energy and as fuels . Compared to the ecological biomass terms, the energy-technical biomass term is much narrower. First of all, it refers exclusively to animal and vegetable substances, but never to microbial substances. And secondly, within animal and vegetable substances, it only includes those substances that can be used for energy purposes.

"Biomass: organic substances of a biogenic, non-fossil type for energetic use. Use in biomass heating systems. "

- Federal Association of Agricultural Employers' Liability Insurance Associations : Biomass heating systems . Kassel, 2008, p. 3.

“Biomass within the meaning of this ordinance are energy sources made from phyto- and zoo-mass. This also includes secondary and by-products resulting from phyto- and zoo-mass, residues and waste, the energy content of which comes from phyto- and zoo-mass. "

- Federal Ministry of Justice in cooperation with juris GmbH : Ordinance on the generation of electricity from biomass (Biomass Ordinance - BiomasseV) . Berlin 2001, p. 1.

The following forms of biomass that are considered in terms of energy technology are named: wood pellets , wood chips , straw , grain , waste wood , plant debris , biodiesel and biogas . Energy-relevant biomass can therefore be in gaseous, liquid and solid form.

Types of biomass

criteria

Biomass can be classified according to three different criteria. The three criteria and the respective types of biomass result from the various ecological biomass terms.

Criterion: water content

  • Fresh biomass: The biomass including the water it contains.
  • Dry biomass: The biomass without any water it may contain.

Criterion: origin of the biomass

  • Phytomass: The biomass comes from plants.
  • Zoomasse: The biomass comes from animals.
  • Microbial Biomass: The biomass comes from microorganisms (including fungi).

Criterion: vitality of the biomass

  • Living biomass: The biomass is located on / in living organisms.
  • Dead biomass: The biomass is on / in dead organisms or has died.

Living biomass

The primary producers are at the base of the formation of biomass . These are organisms that extract low-energy building materials from the inanimate environment and convert them into nutrients. The energy they need for this transformation is also taken from the inanimate environment ( autotrophy ). Inanimate energy sources for autotrophy are light ( photoautotrophy ) and certain chemical reactions ( chemoautotrophy ). The most widespread, multicellular primary producers on the mainland are the photoautotrophic land plants . The most common primary producers in the light-flooded sea areas are microscopic and therefore belong to the phytoplankton .

Food pyramid: 1000 kg of grain per year are converted into 90 kg of body weight by 3000 field mice . A common buzzard eats 3000 field mice per year and weighs 1 kg. Thus only a small part of the biomass remains in the next trophic level.

Consumers feed on the primary producers and / or on other consumers. The consumed organisms or organ parts are digested by the consumers and then used to build up their own biomass. In this way, for example, plant biomass is converted into animal biomass (→ e.g. processing ).

Not all of the consumed biomass can be completely digested. A certain proportion is excreted largely undigested. In addition, consumers use most of the digestible biomass for energy supply ( catabolism ). Only a small part is converted into the body's own biomass ( anabolism ). As a result, consumers only provide a small part of the total biomass.

Dead plants, animals and other living beings are also referred to as biomass. Such biomass is in turn broken down by destructors and used to build up its own biomass. Ultimately, destructors lead to the greatest possible degradation of biomass. In the end, those low-energy building materials are released again, from which the primary producers can build new biomass: The material cycle is closed.

Dead biomass

A large proportion of the biomass is made up of dead organ (ism) ical matter. Dead biomass is commonly called inventory waste .

In plants, the dead biomass ( dead phytomass ) consists of dead or repelled parts of the plant. These include broken / torn leaves, side shoots, twigs and branches. In addition, the fallen leaves , excess pollen and spermatozoids, non-germinated plant spores and seeds, as well as remaining fruits. However, whole plants can also die off. Larger dead branches and whole dead trees are called deadwood .

In animals, the dead biomass ( dead zoo mass ) also consists of dead or shed body parts. This includes hair, feathers and scales that have fallen out or torn out. Likewise exuviae , cocoons , cocoon remains , egg shells, membranes residues and repelled placentas . In addition, torn and separated body parts (→ autotomy ) and remaining sperm (in the case of external fertilization → fish milk ). However, whole animals can of course also die off (→ carcasses ) or unfertilized eggs can be produced. The dead zoo mass still includes many excretions , first and foremost the excrement .

Dead phytomass from land plants (excluding dead wood) is called litter . Over time, litter forms a thick layer on the earth's surface (litter layer / litter layer). Dead zoom mass is also embedded in the scattering layer.

The waste that accumulates in bodies of water is called detritus .

In addition to the term dead biomass, there is also the term necromass . In the specialist literature, however, both terms are only used synonymously in a few cases. In other cases, however, necromass refers exclusively to dead phytomass.

Part of the dead biomass is deposited in areas where destructors can hardly exist. In such poorly destructive areas there is usually an extreme lack of oxygen ( hypoxia ) or even a lack of oxygen ( anoxia ). Because of the severely limited destruction activity, large amounts of hardly decomposed biomass can gradually accumulate in those areas. This hardly decomposed biomass becomes the raw material for fossil fuels . These include natural gas and oil as well as the two biogenic sediments coal and peat . Fossil fuels are no longer viewed as biomass. The same applies to kerogen and to the other biogenic sediments. It is true that biogenic limestones , biogenic pebbles and biogenic phosphorites can also be traced back to certain forms of dead biomass. However, they are also not counted as biomass.

Composition of biomass

Biomass consists primarily of living or dead organisms, which in turn consist of a large number of different compounds . The quantitatively most important compounds can be grouped into three compound classes:

In addition, there are many other compounds in biomass, such as lignin , nucleotides and others.

With regard to the chemical elements it contains , biomass mainly consists of carbon , oxygen , hydrogen , nitrogen , sulfur , phosphorus , potassium , calcium and magnesium , and to a lesser extent iron , manganese , zinc , copper , chlorine , boron , molybdenum and other elements.

Most of the biomass is made up of living or dead plants. Living plants are mainly made up of carbohydrates such as cellulose. Perennial plants form wood , which mainly consists of lignocellulose , a combination of lignin and cellulose. After plants die, easily degradable compounds such as proteins, fats and mono- and oligosaccharides are usually broken down quickly. Compounds such as cellulose and lignocellulose that are difficult to degrade to very difficult persist much longer. In the case of lignin, this is due to the high proportion of benzene rings in the chemical structure.

amounts

The amount of biomass is usually given as its dry biomass. The units used are gram (g), kilogram (kg), ton (unit) (t) and gigaton (10 9 t). Instead of the dry matter, their carbon content is increasingly being stated, as this makes it clear how much carbon is stored in biomass. Furthermore, it can be estimated how much inorganic carbon (in carbon dioxide and hydrogen carbonate ) is removed from the inanimate environment annually and re-incorporated into biomass by living beings.

Quantities according to the ecological biomass concept

Proportion of the biomass of all land-living mammals

The amount of biomass in the entire ecosphere remains difficult to estimate. There are different and sometimes very contradicting statements in the literature. There are four main points of disagreement:

  • The amount of biomass that currently exists globally.
  • The amount of biomass that is newly produced globally each year.
  • The proportion of biomass that is produced annually globally by terrestrial and marine organisms on the one hand.
  • The ecological biomass term that is used. It shows which substance mixtures are actually considered biomass and which are included in the estimates.

Different scientists can sometimes deliver very different biomass values ​​for the same groups of living beings. These contradictions arise because different scientists do not always use the same ecological biomass terms. For example, the values ​​of fresh biomass are much higher than those of dry biomass. The water it contains contributes significantly to the weight, but is not counted as biomass by some authors because they limit the term biomass to organic substances. Likewise, the biomass values ​​are lower if only the biomass is seen in living organisms and the huge amount of dead biomass is not taken into account.

The first estimate of the total biomass of the terrestrial ecosphere was made by Vladimir Ivanovich Vernadski . He stated their mass as 10 20 to 10 21 g (grams). The global biocenosis should produce more than 10 25 g of new biomass annually. However, most of it is dismantled immediately. Sixty-two years later, for example, the Russian marine researcher Evgenii Aleksandrovich Romankevich estimated the global biomass to be 7.5 · 10 17 g of bound carbon. He measured the annually newly formed biomass at 1.2 · 10 17 g. According to other information, the total mass of all living beings should be 1800 · 10 15 g, that of animal life 3.5 · 10 15 g and that of humans 0.4 · 10 15 g. In addition to these three examples, there are a number of other estimated values ​​in the literature.

The vast majority of global biomass is formed by autotrophic organisms, especially cyanobacteria , algae and land plants . All three groups practice a certain form of autotrophy, which is called photohydroautotrophy (→ change of substance and energy ). They represent a living biomass of 740 · 10 15 g of bound carbon. More than 99 percent of the total photohydroautrotrophic biomass formed should be present in land plants, with a biomass of 738 · 10 15 g of bound carbon.

It is estimated that around half of the world's annual primary production is carried out by marine algae and that around 50 · 10 15 g of carbon are bound. However, the amount of biomass produced in the marine environment could also be more than ten times higher. Every year 45–50 · 10 15 g of carbon from the carbon dioxide of phytoplankton are supposed to be bound. If the phytoplankton of the oceans didn't convert that much carbon dioxide into biomass, the carbon dioxide concentration in the atmosphere would probably be 565 ppm instead of 365 ppm. In the world's oceans, the dead phytoplankton sinks to the ocean floor. It takes about 15% or 8 · 10 15 g of the carbon previously assimilated near the surface with it into the depths. Other scientists estimate the amount of marine biomass formed annually at around 530 · 10 15 g, which is more than ten times higher. Of these 530 gigatons, around three percent, or 16 · 10 15 g, sinks as sea ​​snow down to sea ​​areas far from the sun. In the lightless depth, this waste becomes the basis of its own ecosystems. Dead biomass, which is under high pressure in the deep sea, can eventually turn into crude oil or natural gas after many millennia. These products of geological transformation are no longer counted as biomass.

According to a study published in 2018 by the Weizmann Institute of Science (Israel), the earth's biomass is distributed among the various forms of life as follows:

  • 82% plants
  • 13% microorganisms
  • 5% animals and fungi (humans make up 0.01%)

With regard to the anthropogenic influence on the biosphere , the current distribution of the biomass of all land mammals is instructive:

  • 60% domestic and farm animals
  • 36% people
  • 4% wildlife

According to this, 15 times as many domestic and farm animals (calculated in weight) as wild animals live on earth today, and humans themselves make up more than a third of the biomass of all mammals. The distribution of birds is similarly unusual: 70% are poultry .

Of all mammals living on earth, 60% belong to the "farm animals" kept by humans; most of them are cattle and pigs. Without including humans in the calculation, the proportion of "farm animals" in all mammals would even amount to almost 94%. The scientists paint a similarly terrifying picture for birds: only 30% of all birds live in the wild. 70% of them are poultry kept for human consumption.

The Israeli scientists analyzed hundreds of studies for their work. Satellite data and data from gene sequencing were also used. However, the authors also point to considerable uncertainties in this study, particularly with regard to the microorganisms.

The authors of the study state that some of their estimates remain significant uncertainties. This is especially the case with bacteria that live deep under the earth's surface. Nonetheless, the study is groundbreaking as the first of its kind.

“This study is [...] the first comprehensive analysis of the biomass distribution of all organisms on earth. Above all, it provides two important insights: First, that people are extremely efficient at exploiting natural resources. They have killed wild mammals on almost every continent and in some cases exterminated them - for food or for fun. And second, that plant biomass is overwhelmingly dominant from a global perspective. "

- Paul Falkowski, Rutgers University (USA)

The figures mentioned so far deal with the biomass of the entire earth or at least very large areas (land, sea, deep sea). However, there are also a great many scientific publications that deal with the biomass of smaller ecosystems or individual populations. Your biomass information will of course be more accurate the easier it is for people to reach the examined ecosystems ( forest example ). Biomass volume and biomass production of difficult to study ecosystems and biocenoses are therefore comparatively more difficult to estimate (example plankton ). And so far it has hardly been possible to estimate the volume of biomass and biomass production of purely microbial and difficult-to-access ecosystems. Indeed, a significant proportion of the total terrestrial biomass - so far almost completely unnoticed - is supposed to be in the cells of archaea and bacteria that inhabit deep ocean sediments.

In summary, it can be said that the biomass for individual ecosystems and populations can be determined with little difficulty and a certain accuracy. Greater uncertainties arise when the biomass of the entire ecosphere is to be given. The main uncertainties here are in the little explored areas of the seas and, above all, in the as yet hardly explored, purely prokaryotic biocenoses. On the other hand, it is certain that the vast majority of the living biomass of the ecosphere consists of autotrophic organisms - and that the total biomass of the ecosphere comprises at least several tens of gigatons of carbon.

Quantities according to the energy technology biomass concept

Depending on the factors that are taken into account, different biomass potentials result.
( see also article biomass potential )
( for the potential of bioenergy see also article bioenergy )

The volume of agricultural waste is estimated at 10-14 km³. That is an average of 42.5 t of new biomass per hectare every year. In natural forests, this production is offset by the degradation of biomass (dead wood, leaves, etc.) in a similar dimension, so that there is no net increase or decrease. The biomass produced annually in the forests alone contains 25 times the energy of the oil produced annually.

An average 80-year-old beech is around 25 meters high and has a dry matter of 1.8 tons of wood. About 0.9 tons of carbon are bound in it. The amount of energy in the wood of this beech corresponds to around 900 liters of heating oil. A living beech tree generates the oxygen demand for 10 people.

For technical, economic, ecological and other reasons, only part of the biomass can be made available for human use, so that its potential contribution to the energy supply is limited.

The energy of the plant-based food produced annually for the world's population corresponds to about 20 exajoules. Remnants of food production (rice, wheat, corn, sugar cane) that cannot be used by the human organism such as stalks, pods etc. with a theoretically recoverable energy content of approx. 65 exajoules are currently simply burned. The burned biomass from leftovers from food production amounts to around 2 gigatons per year. At least 38 exajoules would be energetically usable annually.

The theoretically usable biomass potential of the earth corresponds to an energy content of 2000 to 2900 exajoules of the land mass and about 1000 exajoules in waters and seas. Technically one could use about 1200 exajoules annually. However, some technically possible uses have limits in terms of economic concerns. After weighing the costs, only about 800 exajoules per year would be economically usable. The worldwide consumption of primary energy (crude oil, natural gas, coal, atomic energy, renewable energy) was about 463 exajoules in 2004.

Use of biomass

Biomass has an important function for people as food and as feed in animal breeding, raw material ( renewable raw material - abbreviated as Nawaro ) and energy source (so-called bioenergies such as firewood , biofuel etc.). Humans currently use a considerable part of the biomass available worldwide. But biomass that is not used by humans also has an important function in ecosystems , for example as a nutrient or habitat for various living things. In addition, large amounts of carbon are stored in biomass, which are released as the greenhouse gas carbon dioxide (CO 2 ) when the biomass is broken down. Biomass therefore plays an important role for the climate.

advantages

  • The use of renewable raw materials can serve to conserve raw material resources such as crude oil . If the renewable raw materials are provided regionally, the political and economic dependence, for example on countries with large oil deposits, can decrease.
  • Renewable energies from renewable raw materials enable CO 2 -neutral or lower CO 2 energy generation.
  • Renewable raw materials can be stored relatively cheaply.

disadvantage

  • If the use of biomass is extended to previously unused natural areas (e.g. clearing forests), ecosystems can be destroyed and biodiversity endangered. Large quantities of CO 2 are also released, especially during slash and burn operations .
  • The increasing energetic and material use can lead to competition for land compared to food production. ( see article bioenergy and biofuel )
  • In agricultural biomass production, fertilizers (nitrogen, phosphorus, potash fertilizers and other fertilizers) are used, which leads to greenhouse gas emissions ( nitrous oxide from nitrogen fertilizers), nitrate input (NO 3 - ) into groundwater, nutrient input into surface water ( eutrophication ) and others Damage leads. The use of pesticides can damage the environment and health.
  • By expanding the irrigation of agricultural land, water resources are used that are ecologically important or that ensure drinking water supplies elsewhere.
  • The combustion of solid biomass (e.g. wood) without special measures is associated with higher pollutant emissions ( carbon monoxide , soot , PAH ) than when burning oil or gas.
  • Burning in systems removes dry and dead wood from the natural cycle and the carbon stored in the sediments of the forest floor over decades is quickly released into the atmosphere as CO 2 .
  • Harvesting, processing and transporting is associated with large consumption of fossil energy sources and electrical energy as well as extensive mechanical expenditure.

Use of biomass in Germany

Most of the biomass used in Germany is used to produce food and feed , as a renewable raw material for material use ( timber , starch and the like) or for classic energetic use in the form of firewood (also in the form of agricultural cultivation in short rotation plantations ). The Biomasse Ordinance (BiomasseV) contains legal definitions .

For several years there has been a significant increase in the use of biomass. The main reason is the increasing use of energy ( bioenergy ). The Renewable Energy Sources Act (EEG) promotes, among other things, the use of biomass to generate electricity, such as the burning of wood in biomass heating plants and biomass heating plants , or the fermentation of liquid manure and silage from energy crops in biogas plants and subsequent conversion of the biogas into electricity .

Biofuels are supported by the state through reduced tax rates ( Energy Tax Act ) and blending quotas ( Biofuel Quota Act ), as they conserve fossil raw materials, have less impact on the climate and reduce dependency on imports.

Sustainable cultivation, i.e. compliance with ecological and social criteria, is ensured by the Biomass Electricity Sustainability Ordinance (BioSt-NachV): Manufacturers of bioenergy or biofuels must prove that the products have been manufactured in an environmentally, climate-friendly and nature-friendly manner. Evidence is provided as part of certification by accredited certification bodies such as Bureau Veritas or the Technical Monitoring Association . This avoids ecological damage, such as the energetic use of palm oil from deforested rainforest areas.

The generation of heat from bioenergy is promoted by the Renewable Energies Heat Act (EEWärmeG), especially the use of biomass for pellet heating and wood chip heating .

The use of wood and straw for heating purposes in Germany increased between 1995 and 2006 from 124 petajoules to 334 petajoules. The production of biodiesel increased from 2 petajoules in 1995 to 163 petajoules in 2006. Biogas production increased from 14 petajoules in 1995 to 66 petajoules in 2006. For comparison: The total mineral oil consumption in Germany was 5179 petajoules in 2006. In electricity generation, the share of biomass and biogenic waste increased from 670 GWh and 1,350 GWh in 1995 to 14,988 GWh and 3,600 GWh in 2006. Electricity generation In 2006, biomass roughly corresponded to electricity generation from hydropower.

In 2013, energy crops were grown on more than a tenth of arable land in Germany as a fermentation substrate for biogas plants.

See also

literature

  • Sustainable bioenergy: status and outlook - final summary report on the project "Development of strategies and sustainability standards for the certification of biomass for international trade" by Öko-Institut / IFEU , i. A. of the Federal Environment Agency. Darmstadt / Heidelberg 2010. (PDF file; 343 kB).

Web links

Wiktionary: Biomass  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ V. Vernadsky: The Biosphere. New York 1998, ISBN 0-387-98268-X , p. 70.
  2. ↑ VI Vernadsky: La Géochimie. Paris 1924.
  3. ↑ VI Vernadsky: биосфера [Biosphere]. Leningrad 1926.
  4. ↑ R. Demoll: Considerations on production calculations . In: Archives for Hydrobiology. 18, 1927, p. 462.
  5. ↑ VG Bogorvo: Seasonal changes in biomass of Calanus finmarchicus in the Plymouth Area in 1930. In: Journal of the Marine Biological Association of the United Kingdom (New Series). 19, 1934, p. 585 doi: 10.1017 / S0025315400046658 (pdf; 7.3 MB)
  6. ^ A. Christian, I. Mackensen-Friedrichs, C. Wendel, E. Westdorf-Bröring: Metabolic physiology. Braunschweig 2006, ISBN 3-507-10918-2 .
  7. ↑ VG Bogorov: Seasonal Changes in biomass of Calanus finmarchicus in the Plymouth Area in 1930. In: Journal of the Marine Biological Association of the United Kingdom (New Series). 19, 1934, pp. 585–612 doi: 10.1017 / S0025315400046658 (pdf; 7.3 MB)
  8. ↑ VG Bogorov: Seasonal Changes in biomass of Calanus finmarchicus in the Plymouth Area in 1930. In: Journal of the Marine Biological Association of the United Kingdom (New Series). 19, 1934, p. 589. doi: 10.1017 / S0025315400046658 (pdf; 7.3 MB)
  9. ^ NA Campbell, JB Reece: Biology. Munich 2006, ISBN 3-8273-7180-5 , pp. 1414, 1500.
  10. ↑ VG Bogorov: Seasonal Changes in biomass of Calanus finmarchicus in the Plymouth Area in 1930. In: Journal of the Marine Biological Association of the United Kingdom (New Series). 19, 1934, p. 589. doi: 10.1017 / S0025315400046658 (pdf; 7.3 MB)
  11. ^ FW Stöcker, G. Dietrich (Ed.): Brockhaus abc Biologie. Leipzig, 1986, ISBN 3-325-00073-8 , p. 105.
  12. ^ NA Campbell, JB Reece: Biology. Munich 2006, ISBN 3-8273-7180-5 , pp. 1414, 1500.
  13. ^ Meyers Taschenlexikon Biologie . Mannheim / Vienna / Zurich 1988, ISBN 3-411-02970-6 , p. 100.
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  17. ↑ Martin Kaltschmitt, Hans Hartmann, Hermann Hofbauer: Energy from Biomass - Fundamentals, Techniques and Processes . 2nd Edition. Springer, Berlin 2009, ISBN 978-3-540-85094-6 , pp. 2–3 ( limited preview in Google Book search).
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  24. ↑ Federal Association of Agricultural Professional Associations eV: Biomass heating systems. Kassel 2008, p. 3 (pdf)
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  26. ↑ Federal Association of Agricultural Professional Associations eV: Biomass heating systems. Kassel 2008, p. 3 (pdf)
  27. ↑ Federal Ministry of Justice in cooperation with juris GmbH: Ordinance on the generation of electricity from biomass (Biomasse Ordinance - BiomasseV). Berlin 2001, pp. 1–2 (pdf)
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  32. ↑ Florian Nagel: Electricity from wood through the combination of gasification and solid oxide fuel cells. Ph.D. Thesis. Swiss Federal Institute of Technology, Zurich 2008.
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  34. ^ V. Vernadsky: The Biosphere. New York 1998, ISBN 0-387-98268-X , p. 70.
  35. ^ V. Vernadsky: The Biosphere. New York 1998, ISBN 0-387-98268-X , p. 72.
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  37. ^ W. Brefeld: Life on earth and its mass. 2009–2012.
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  42. ^ W. Probst: Algae - omnipresent and versatile. In: teaching biology. 365, 2011, p. 6.
  43. ↑ CR McClain: Lush variety despite a lack of food. In: Spectrum of Science. 11, 2011, p. 68.
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