Wood pellet

from Wikipedia, the free encyclopedia
Wood pellets
Pelletizing machine
Ring die of a pelleting machine

As pellets rodlike be pellets having a diameter designated by less than 25 millimeters, which completely or predominantly of wood or sawmill by-products are produced. Wood pellets are primarily used as fuel, comparable fuel pellets are straw pellets or other straw pellets , peat pellets, pellets made from olive pits and pressed olive pomace , coconut shells or other biogenic residues .

Pelleting offers various advantages over other biogenic solid fuels , such as automated use as fuel in special pellet heating systems (for further advantages, see Pellet Purpose ).

Pressed wood pieces from 25 millimeters in diameter are called wood briquettes , for which other requirements sometimes apply.

Wood pellets are burned in small firings, in industrial furnaces and in power plants.


Wood pellet production began in North America as early as the 1930s . In 1978 the aircraft technician Perry Whitfield built a pellet stove in the USA in the wake of the 1973 oil price crisis to thermally utilize the litter from his rabbit husbandry. It achieved less dust emissions in the exhaust gases than with log wood stoves. When he presented his invention at the annual Wood Heating Alliance Show ( Reno , Nevada ) in 1984 , he received over 1,000 stove orders within four days. From 1985 onwards, dried wood pellets were used in Sweden to fire power stations because the transport and burning of wet wood chips would have been too expensive. From 1993, Austrian began boilers bauer pellet stoves to the US to export and at the same time the market to develop in Austria.


The wood pellets are usually produced near the source of the raw material. These are z. B. sawmills and planing mills in which wood waste ( wood chips , sawdust and shavings ) is a by- product . About 30% of the pellets also be produced from round wood of lesser quality ( English low quality roundwood invention).

The raw materials are first crushed, for example using a hammer mill . Biomass heating plants or biomass heating power plants connected to the pellet plant or wood processing can supply the heat for drying the raw materials.

The pellets are formed in a pelletizing plant (pellet press , see flat die press ). The material is pressed under high pressure through a steel die (round or flat die) with holes in the desired pellet diameter (6 to 10 mm depending on the die). The pressure heats the wood and liquefies the lignin contained in the wood so that it acts as a binding agent. It may be necessary to add more binding agent ( starch or molasses ) in proportions of 0.2 to 2%. As it emerges from the die, a doctor blade cuts the strands into pellets of the desired length (10 to 30 mm).

The energy expenditure in pellet production is usually around 2.7% of the energy content when using dry waste wood. If, on the other hand, moist industrial or residual forest wood is used for pelleting, the energy required can be between 3 and 17%.

Properties and standardization

ISO 17225-2 “Biogenic solid fuels - fuel specifications and classes” applies to wood pellets. Part 1 “General Requirements” of the standard applies, and Part 2 “Classification of wood pellets” for pellets for non-industrial use. Part 2 lays down more stringent specifications, as the small combustion systems used here are usually equipped with less complex controls and exhaust gas purification, are not operated by experts and are located in an inhabited area.

Wood pellets for industrial use

Logo of the German Institute for Standardization DIN ISO 17225-2
Area Fuels
title Solid biofuels - Fuel specifications and classes - Part 1: General requirements
Latest edition 2014-09

Wood pellets are traded in five size classes (see table) and two water content classes M10 and M15 with a maximum of 10 or 15% water content. Classes are also defined for ash content (A), mechanical strength (DU), fine material content (F) and bulk density (BD) as well as for sulfur (S), nitrogen (N) and chlorine content (Cl). The calorific value Q and a possible content of additives must be specified, the ash softening temperature DT should be specified. The bulk density must be at least 600 kg / m³; no limit values ​​are specified for the other properties mentioned above.

Size class diameter length Water content class Water content
D06 6 mm ± 1.0 mm 3.15 mm to 40 mm, 1% up to 45 mm M10 Max. 10%
D08 8 mm ± 1.0 mm 3.15 mm to 40 mm M15 Max. 15%
D10 10 mm ± 1.0 mm 3.15 mm to 40 mm
D12 12 mm ± 1.0 mm 3.15 mm to 50 mm
D25 25 mm ± 1.0 mm 10 mm to 50 mm

Wood pellets for non-industrial use

Logo of the German Institute for Standardization DIN ISO 17225-2
Area Fuels
title Solid biofuels - Fuel specifications and classes - Part 2: Wood pellets for non-industrial use
Latest edition 2014-09

Only sizes D06 and D08 in water content class M10 are traded for non-industrial use. The bulk density must be at least 600 kg / m³, the fine material content must not exceed 1%, the additive content maximum 2%. Three property classes are defined. Pellets of classes A1 and A2 are made from freshly harvested wood or chemically untreated wood residues, in the case of A1 from material with a low ash and nitrogen content, in the case of A2 with a slightly higher ash and nitrogen content (e.g. pellets from full trees, residual forest wood or Bark). Class B pellets can also consist of industrial waste wood and chemically untreated used wood and may have a higher ash and nitrogen content. In addition, a minimum calorific value and a minimum strength are specified. The strength test according to EN 15210 includes a ten-minute treatment in a rotating box with a baffle plate. Before and after this treatment, the sample is sieved through a perforated plate with holes 3.15 mm in diameter; only the retained material from the first sieving is tested. At least the specified mass fraction must be retained during the second sieving.

property Class A1 Class A2 class B
Ash content A0.7 Max. 0.7% A1.2 Max. 1.2% A2.0 Max. 2.0%
Nitrogen content N0.3 Max. 0.3% N0.5 Max. 0.5% N1.0 Max. 1.0%
strength DU97.5 min. 97.5% DU97.5 min. 97.5% DU96.5 min. 96.5%
calorific value Q16.5 > 16.5 MJ / kg Q16.5 > 16.5 MJ / kg Q16.5 > 16.5 MJ / kg

Limit values ​​are set for sulfur, chlorine and heavy metal contents. For ash melting behavior, the temperature at the beginning of the shrinkage (SST), softening temperature (DT), hemisphere temperature (HT) and flow temperature (FT) should be given.

The “ENplus” and “EN B” quality seals, trademarks of the European Biomass Association , are awarded by national pellet associations to companies that manufacture, trade or transport pellets via the European Pellet Council . The requirements for pellets for the ENplus-A1, ENplus-A2 and EN-B seals basically correspond to the corresponding qualities of the ISO 17225-2 standard, but the ash softening temperature should also be specified. In addition, the entire chain up to the end customer is recorded and corresponding storage and transport conditions are prescribed. Continuous reserve samples (except for delivery in 15 kg bags) must be taken and the traceability of all deliveries back to the manufacturer must be guaranteed. In addition, annual inspections are carried out on the producers by the certifying body; in the case of retailers, the inspection is carried out every three years.

Another established certification is on the market with the "DINplus" quality mark, a trademark of DIN CERTCO mbH. In addition to the requirements of the DIN EN ISO 17225-2 standard, there are additional requirements for the product. The fine content must not exceed 0.5% and not, as in the standard, 1%. Annual reviews of the producers are carried out.

Typical properties of wood pellets for small combustion systems

Wood pellets have the following properties:

  • Energy density of around 4.8 kWh / kg (17,000 kJ / kg), 2 t pellets contain the energy of around 1000 l heating oil (equivalent)
  • Bulk density of around 650 kg / m³
  • Water content below 10%
  • Ash content of less than 0.5% for high-quality pellets

Other important properties and quality features are the diameter and length of the pellets, the content of certain elements (sulfur, chlorine), the abrasion resistance, the raw materials used and others.

Older standards and certifications: ÖNORM / DIN / SN - DINplus / SWISSPELLET / PVA

Logo of the German Institute for Standardization DIN 51731
Area Fuels
title Testing of solid fuels - pellets made of untreated wood - requirements and testing
Brief description: Pellets
Latest edition 1996-10 (withdrawn)
ÖNORM M 7135ff
title ÖNORM M 7135: Requirements and test regulations for pellets
ÖNORM M 7136: Requirements for transport and interim storage
ÖNORM M 7137: Pellet storage at the consumer or end customer
Area Pellets made of natural wood or natural bark . Standardization area: ON-K 241 "Energy from solid biomass"
Regulates Pellets HP1 "ÖNORM M 7135 tested" and their transport and storage
Publishing year ÖNORM M 7135: 2000 11 01
ÖNORM M 7137: 2002 06 01
ÖNORM M 7137: 2003 10 01
Remarks Corresponds to: DINplus (partially)

Until 2011, the identical standards DIN 51731 and SN 166000 were relevant for pellets made from untreated wood in Germany and Switzerland , and in Austria ÖNORM M7135 to M7137. In comparison, the Önorms set higher mechanical requirements and also regulated transport and storage, while the DIN and SN also set heavy metal limit values. The seal of approval of the Pelletverband Austria, the DINplus certification (still on the market, also referenced to DIN EN ISO 17225-2) and the SWISSPELLET label resulted in extensive standardization, as the higher requirements of the standards mentioned were applied .

Data according to ÖNORM M 7135 requirements and test provisions or DINplus:

The SWISSPELLET label has existed for Switzerland since 2002. Only pellets that have been produced in Switzerland are available under this label.

Since the quality of the wood pellets can suffer from improper transport or storage, ÖNORM M 7136 regulates transport and interim storage from the manufacturer to the end customer. The ÖNORM M 7137 pellet store regulates the storage at the consumer and should "ensure operational safety , fire protection , the static requirements and the maintenance of the pellet quality".


The importance of wood pellets has increased steadily in Germany and Europe in recent years. In 1999, only 800 pellet heating systems were installed in residential buildings in Germany. The number rose to 27,000 by 2004, to around 100,000 by 2008 and to 180,000 in 2013. In 2016, almost 422,000 pellet heating systems were installed in Germany.

In Austria there were 7,000 pellet boilers in operation in 2000, and more than 100,000 in 2012. Worldwide pellet production increased from 2.5 million tons in 2002 to 23 million tons in 2012.

Fuel costs

Since the pellets are made from by-products of the sawing industry, the production is related to the construction industry, the general economic situation (packaging wood) and the amount of round wood ( damaged wood from storm or beetle calamities ).

In the past few years, there has been strong growth in supply and demand on the pellet market, with a varying time lag. After an initially quite high price after the market launch at the end of the 1990s, a phase of relatively low prices of 3.50 cents / kWh in Germany followed from 2002 to 2005. This was followed by several months of high pellet prices of more than 5 cents / kWh in winter 2006 / 07 due to supply bottlenecks. Since 2007, the manufacturers have further expanded their capacities, so that the retail value has fallen to a level between approx. 3.50 and 4.50 cents / kWh. In 2018, the price per heating capacity, calculated per ton, was around 5.20 cents / kWh.

Cost comparison

To assess the profitability of a pellet heating system, the specific costs of storage and combustion must be taken into account in addition to the fuel costs. In particular, the lower specific calorific value requires a higher storage volume. A pellet supply, based on the specific calorific value, should therefore be at least 10% cheaper than the storage of heating oil or at least 20% cheaper than the supply of heating gas free of storage costs. In Austria, the cost advantage of pellets over extra light heating oil has been between 40 and 56% since 2010.

Price development

Delivery of wood pellets in tank trucks
  • Until spring 2004, the price of pellets was about the same as the price of heating oil and around 30% cheaper than natural gas. After that, the price for pellets rose only moderately, while the price for heating oil and natural gas rose sharply. Based on the Austrian prices, the heating cost savings at the end of 2005 were 40 to 50% compared to oil. The price fluctuated between higher prices in winter and lower prices in summer.
  • From the summer of 2006, there was for the first time no decline, but a continuous price increase. The price for DIN-Plus pellets in Germany in July 2006 was an average of € 206 per ton. In Austria the price rose to up to € 250 in autumn 2006 and leveled off at € 255 in December.
  • Due to the extremely mild winter of 2006/07, but especially after the wind break caused by winter storm Kyrill on 18/19. January 2007, and the subsequent oversupply of wood, prices began to fall significantly again, to an average of € 185 per ton in spring 2007, and stabilized by the massive expansion of production capacities at € 180–200 until autumn.
  • In 2008, the pellet price in Austria did not exceed € 200 per ton and in mid-2008 was between € 155 and € 175.
  • In 2010, the annual average price for a delivery of 5 tons of loose goods within a 50 km radius in Germany was 228.45 € per ton and rose in 2011 to 241.41 € per ton. With a calorific value of 4.9 kWh / kg, this corresponds to 4.66 ct (2010) or 4.93 ct (2011) per kWh. In June / July the price per ton is up to 10% lower.
  • In December 2012 wood pellets cost an average of € 256.24 per ton in Germany. The price in Austria was € 243.2 per ton in September 2014, and CHF 391.68 / t in Switzerland, which corresponds to € 324.23 per ton.
  • The price development in Austria compared to natural gas and wood pellets can be objectively observed using the Austrian price indices for the products: In January 2013, the Austrian gas price index was 143.75 compared to the January 2006 base value, i.e. H. the gas price rose in these seven years by 1.44 times (for clarification of the usual price fluctuations see gas price development and). The pellet price index was 136.80 in September 2014, i.e. H. the pellet price increased by 1.37 times in comparison. From 2002 to 2019 prices in Austria rose by around 40%.

Security of supply

In Germany, the production capacity for wood pellets (2.5 million tons in 2009) exceeded consumption in 2009 by approx. 230%.

  • In 2003, with increasing demand in Sweden, 1.5 million tons and Austria 280,000 tons of pellets were produced, which was quite sufficient at the time.
  • Due to the large increase in pellet heating systems, there were delivery bottlenecks for pellets across Europe in winter 2005/2006. As every year, the pellet producers delivered large quantities to Dutch power plants in the summer. In 2006 this was reduced and new storage capacities were built.
  • The main problem is security of supply, since other countries are also promoting the use of pellets: The Czech Republic, for example - the traditional supplier for the Austrian market - is increasingly covering its own needs, and Italy is also developing into an important customer who is willing to pay relatively high prices to pay. The enormous price increases in 2006 can be seen in this context, but also with the exceptionally long and snowy winter of 2005/2006.
  • The high-priced fuel market also leads to (local) bottlenecks in the cellulose industry and for chipboard manufacturers who use the same raw material, and to increasing industry competition. However, the need for cellulose could be reduced in part by increasing the use of recycled paper.

Worldwide (beginning of 2008) 14 million tons of pellets are produced.

Situation in Austria

After the commissioning of new plants, the production capacities in Austria are around 900,000 tons per year compared to 500,000 tons at the beginning of 2006 and are twice as high as the domestic demand. Due to the last, mild winter, there are high storage reserves, whereby the - with regional hotspots - large amounts of damaged wood by Kyrill 2007, Paula and Emma 2008 are to be used through cooperative storage without great loss of value. The Scandinavian countries and increasingly the EU eastern states are also developing into pellet exporters in Europe. In Austria, according to the Federal Environment Agency , the demand for pellets in 2020 should be twice as high as in 2010 and at 22,000 TJ, which, taking into account the decline in building heating requirements , corresponds to a supply of 18% of Austrian households.

Dangers from pellets

Pellets are small pressed wood pieces, the inner structures are partially destroyed during pressing. As a result, decomposition products such as carbon monoxide and hydrocarbons can escape from the pellets and accumulate in the air, for example in a pellet silo. The first deaths from serious poisoning have already become known, for example people died in January 2010 in Remscheid and in February 2011 in Horw, Switzerland . They stayed in inadequately ventilated pellet storage rooms and died of poisoning from the invisible and odorless gas carbon monoxide .

Dry pellets swell up to 3.5 times their original volume if they come into contact with water in the event of unplanned water access (flood, fire fighting water, burst water pipes). This can lead to bursting and total damage to bricked pellet storage rooms. According to a report by ORF , swollen pellets stored in the basement during the 2002 flood raised a house two centimeters high. Swollen pellet masses can become very hard after drying, and removal requires high mechanical effort. Increased water contents> 30% can lead to the multiplication of microorganisms (fungi, spores, bacteria) and even cause spontaneous combustion (see also haystack spontaneous combustion ).


Up to 2% pressing aids, mainly starch flour, are used for pressing . If food-grade flours are used, they are no longer available for the production of food.

Internationally there are also wood pellets made from tropical wood ("tropical wood pellet"). According to German environmental aid, there is a risk that the wood produced during clearing could (internationally) be used as raw material for pellets. Solid biomass is not subject to the German Biomass Power Sustainability Ordinance , which only deals with liquid biomass with regard to the generation of bio power. Imports of tropical wood pellets from forest harvesting for the production of electricity in biomass power plants and for other heating purposes are prohibited in the EU area according to the EU Timber Trade Regulation, but a violation is not a criminal offense in Germany, but only an administrative offense.

Critics fear that in addition to " residual forest wood " from forestry, dead wood could also be used for pellet production in order to meet the increasing demand. Researchers and environmental organizations see this as a threat to the richness of species in the forest, as organisms that break down dead wood are then absent from the food chain .

Peter Wohlleben fears that the price pressure will bring more wood scraps, tree tops and tree stumps out of the forest, the heavy machinery required for this would compact the soil and impair the water storage capacity in the soil pores (which in turn would have an impact on the water table). With the tops of the tree, minerals would also be removed that were previously put back into the ground through rotting. The demand for residual forest wood is forcing paper and chipboard manufacturers (the previous buyers for residual forest wood) to use more valuable round wood, the overall increased demand thus leading to rising wood prices. In addition, Wohlleben and others criticize the fact that palm oil is also burned to dry the pellets during production , for which primeval forests in Southeast Asia are cleared. However, there is no evidence for this.

With regard to land use (short rotation plantations, etc.), the German Federal Environment Agency found that wind and solar energy are many times superior to biomass in terms of space efficiency.

The production, drying and delivery of pellets have an impact on the CO 2 balance. Wood pellets achieve a CO 2 balance of 17.4 (industrial waste wood) to 29.8 (forest waste wood) gCO 2 eq / MJ. (Comparison: firewood: 2.62-4.97 gCO 2 eq / MJ; crude oil: 16.8 g CO 2 eq / t).

According to a study by the Austrian Society for Environment and Technology , which compares the capital costs and running costs of fuel-operated heating systems under different heat consumption and energy price scenarios, pellet heating systems pay off with lower or constant energy prices compared to fossil heating systems "only for significantly above-average heat consumers". The more energy is saved through thermal insulation in low- energy houses, for example , the more the high system construction costs affect the total price over the service life. Pellet heating systems then “assuming consistently low energy prices u. U. even represents the most expensive (fuel-operated, note) heating system ”. Pellet boilers, along with log heating, would have the lowest overall costs if the heating costs of fossil fuels rise.

The European Environment Agency warns that increased combustion of biomass in private heating systems could worsen air quality, as wood smoke contains fine dust and soot and can contain toxic substances such as dioxins . From around 2000 to 2005, reductions in fine dust by means of lower-emission forms of wood combustion were nullified by an increase in wood combustion systems. According to an investigation by the Federal Environment Agency, the fine dust emissions from wood combustion systems exceeded the emissions from road traffic (incineration only) by 22,700 tons.


Web links


Commons : wood pellets  - collection of images, videos and audio files
Wiktionary: Holzpellet  - explanations of meanings, word origins, synonyms, translations


Individual evidence

  1. Fuel, especially in the form of pellets, from olive residues and combustible organic and / or inorganic substances , patent specification
  2. olivenpellets.de
  3. Manufacturer of pellets made from tropical wood, coconut shells and oil palm kernels
  4. Wood pellets in the power station market , at pellets.de
  5. Mohammad Ali Abdoli: Wood pellet as a Renewable Source of Energy. Springer, 2018, ISBN 978-3-319-74482-7 , p. 53 ( limited preview in Google book search).
  6. ^ Greg Pahl: Natural Home Heating. Chelsea Green Publishing, 2003, ISBN 978-1-603-58156-1 , p. 280
  7. ^ A b c Rudolf Huber: The history of wood pellets , company website; (PDF file)
  8. a b Jerry Whitfield , at hearth.com (company website)
  9. Steve Wilhelm: Burning ambition fuels stove maker , at bizjournals.com
  10. Pellets - an Austrian success story ; at propellets.at ( lobby organization for the promotion of wood pellets)
  11. D. Thrän et al., 2014, cited in Global Wood Pellet Industry and Trade Study 2017
  12. A Pellet Road Map for Europe . ( Memento of the original from July 5, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF) Brochure on the state and perspective of wood pellet use in Europe, European Biomass Association (AEBIOM), November 2008 @1@ 2Template: Webachiv / IABot / www.aebiom.org
  13. House info: Pellet quality ( Memento of the original from January 15, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved November 2, 2009 @1@ 2Template: Webachiv / IABot / www.hausinfo.ch
  14. ^ New energies, nightmare pellet heating manager-magazin.de of September 10, 2013
  15. ^ The statistics portal: number of pellet heating systems in Germany from 2012 to 2017 ; last accessed on November 5, 2017
  16. Holzpellets.net: The wood pellets price development as a 5-year chart ; last accessed on November 5, 2017.
  17. ^ Expensive heating , ORF Styria, September 14, 2006.
  18. Expert opinion , ORF Carinthia, July 3, 2007
  19. Energy wood market analysis. (PDF, 0.58 MB) (No longer available online.) Klima: aktiv specialist information, August 2013, archived from the original on May 19, 2014 ; Retrieved May 19, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.klimaaktiv.at
  20. ^ Pellet price index. (No longer available online.) CARMEN e. V., archived from the original on January 7, 2012 ; Retrieved October 16, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.carmen-ev.de
  21. Development of the pellet price in Germany. DEPV e. V., accessed December 28, 2012 .
  22. Pellet Prize Austria. (No longer available online.) Archived from the original on October 6, 2014 ; Retrieved October 4, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.propellets.at
  23. Pellet price. eecomm GmbH, accessed on December 28, 2012 .
  24. Austrian gas price index ÖGPI Austian Energy Agency; PDF  ( page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / www.energyagency.at  
  25. Graphic gas prices in Germany in cents / kWh from 1991 ( memento of the original from January 18, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. ( Flash ; 369 kB) @1@ 2Template: Webachiv / IABot / www.fr-online.de
  26. The pellet price index PPI 06 ( Memento of the original dated December 31, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. and corresponding PDF  ( page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.propellets.at@1@ 2Template: Dead Link / www.propellets.at  
  27. Bavaria pellets | A price comparison as to whether and by how much the pellet prices fluctuate. Retrieved February 18, 2020 .
  28. Sustainable use of wood as a resource, p. 62 ff.
  29. Danger from alternative energy. (PDF; 3.9 MB) Nicole J. Seitz, accessed on January 1, 2013 .
  30. Pregnant Monika dead! View online, accessed July 12, 2019 .
  31. Safety instructions for the storage of pellets. Pelletshome.com, accessed May 19, 2014 .
  32. a b c Martin Kaltschmitt: Energy from biomass. Springer-Verlag, 2016, ISBN 978-3-662-47438-9 , p. 548 ( limited preview in Google book search).
  33. https://noev1.orf.at/stories/386690
  34. Thomas Kellner: Renewable Energies in Apartment Buildings. Diplomica Verlag, 2009, ISBN 978-3-8366-7493-5 , p. 29 ( limited preview in Google book search).
  35. Press aids , at pelletshome.com
  36. Wood pellets - on the trail of strength - Holzforschung Austria at holzforschung.at
  37. ^ Pellets from Cameroon
  38. Bioenergy - Opportunity for the 3rd Millennium . German environmental aid
  39. Text of the ordinance on requirements for the sustainable production of liquid biomass for electricity generation
  40. Timber Regulation
  41. Nicolai Kwasniewski: Billionaire business - This is how illegal tropical wood comes to Germany , at spiegel.de
  42. ^ DL Godbold, JD Walmsley: Stump Harvesting for Bioenergy - A Review of the Environmental Impacts . In: Forestry: An International Journal of Forest Research . tape 83 , no. 1 , 2010, ISSN  0015-752X , p. 17-38 , doi : 10.1093 / forestry / cpp028 . ; quoted by Initiative Pro Wildlife eV: The battle for wood pellets - from recycling product to global import hit. ( yumpu.com )
  43. Peter Wohlleben in an interview with Jens Lubbadeh: Consequences of the pellet boom "The forest floor is bleeding out" , at spiegel.de
  44. Dirk Maxeiner: Everything green and good ?. Albrecht Knaus Verlag, 2014, ISBN 978-3-641-14310-7 ( limited preview in Google book search).
  45. Peter Wohlleben in an interview with Jens Lubbadeh: Consequences of the pellet boom "The forest floor is bleeding out" , at spiegel.de
  46. bioenergy
  47. Fehrenbach et al. 2016: Update of the input data and energy balances of essential biogenic energy use paths (BioEm); IFEU Institute for Energy and Environmental Research gGmbH 2016; last accessed in August 2019 at http://www.umweltbundesamt.de/publikationen/aktualisierung-der-eingangsdaten-emissionsbilanzen
  48. Federal Environment Agency: Process-oriented basic data for environmental management instruments; PDF, last accessed in August 2019, p. 7 at http://www.probas.umweltbundesamt.de/php/web2pdf.php?id=%7B9974E2BC-9DDF-4E30-A85D-9A12BB7142E2%7D .
  49. Full cost comparison of heating systems for single-family houses - comparison of the life cycle costs of heating oil, natural gas, pellet and log heating for old single-family houses in nine scenarios , Austrian Society for Environment and Technology [sic], Vienna December 2011, ( oegut.at PDF, last accessed in September 2012), p. 9.
  50. Air quality in Europe - 2017 report apren.pt (PDF); European Environment Society; EEA Report No 13/2017, ISSN  1977-8449 .
  51. Timothy Spence: Doubts cast on biofuels' air quality claims ; at euractiv.com
  52. The side effects of comfort: fine dust from the fireplace and wood stove. Background paper of the Federal Environment Agency, March 2006.