The sustainability of first generation (1G) agrofuels is disputed. Although the EU has put in place specific certification schemes aimed at ensuring that the entire biofuel production and supply chain is sustainable, the problem of indirect land use remains unsolved. 2G fuels are believed to be more sustainable than 1G agrofuels and have been the focus of attention for the last 10 years or so. However, independent experts believe that it might take another 15 to 30 years before 2G fuels can be produced on the industrial scale.

Quite a large number of researchers indulge themselves dreaming about scenarios involving tailor-made algae and microbes to produce fuel for use in car engines and aircraft turbines. In reality however, 1G fuels such as bioethanol and biodiesel made from edible plants such as maize (USA), sugarcane (Brazil), rape, corn (Europe) or palm oil (Asia) still dominate the market. In 2010, the worldwide production of biofuel reached a record high (105 billion litres) and is continuing to rise. As of 2010, the EU has been aiming to raise the percentage of energy from renewable sources in the transport sector to 10 per cent by 2020. In compliance with EU regulations, the German law on biofuel data requires biofuels to account for 6.25 per cent of total fuel demand. From 2015, the system of blending quotas is to change to conform with greenhouse gas reduction targets that will be raised year on year. The goal is to reduce total greenhouse gas emissions from fuel combustion by 7 per cent as of 2020.

In the meantime, numerous 2G fuel production plants worldwide have had to be closed down as they are unable to adapt to large-scale industrial production. Recent examples include Range Fuel (USA, Georgia) and Choren Industries (Germany, Freiberg/Saxony). Other potential cellulosic ethanol producers are shifting focus and are now using maize to produce butanol, which is a major intermediary product for the chemical industry. It has also been reported that potential algal fuel manufacturers have modified their business model (Bullis).

Biomass can be used to produce gaseous and liquid fuels. Biofuels Digest, a widely read online source of biofuel news, lists 135 advanced alternative fuel production plants with a production capacity of around 2.6 billion litres (May 2011). The producers expect a 6-fold increase in production capacity by 2015, which seems to be something of a pipe dream due to the ongoing financial crisis.

The production of hydrogen, a low-emission energy carrier, from biomass is still in an early stage of development. At present, hydrogen is mainly produced from fossil resources using the well-established method of steam reforming. This method is associated with an appalling climate balance. Hydrogen-driven car prototypes have been developed, but the necessary infrastructure is lacking, storage problems are still unresolved and fuel cells are still very expensive and only have a short lifespan. A consortium of public and private partners (Fuel Cells and Hydrogen Joint Undertaking) is working on the market introduction of hydrogen and fuel cells by 2015.

Certain microalgae and cyanobacteria are able to produce hydrogen by way of photosynthesis. The hydrogen yield can be increased through the genetic modification of enzymes that are key in the conversion process. The microbial enzymes that catalyse the cleavage of water into hydrogen and oxygen can be isolated and attached to a suitable membrane using the same procedure as that used for "biobatteries". The biomimetic production of hydrogen involves compounds that are chemically similar to cell constituents. Biological hydrogen (biohydrogen) can be generated by naturally occurring microorganisms using three different metabolic processes - fermentation, anoxygenic and oxygenic photosynthesis. The production of biohydrogen in bacteria and green algae is still in an early stage of development (Bley/Kirsten/Weitze, 31f). 

Two research institutions in Baden-Württemberg are involved in two applied research projects: the Centre for Solar Energy and Hydrogen Research (ZSW) in Stuttgart operates a pilot plant that produces hydrogen from biomass gasification; the Karlsruhe Institute of Technology (KIT) (https://www.biooekonomie-bw.dewww.itc-cpv.kit.edu/53.php) is investigating the production of hydrogen from wet biomass.

Biomethane is produced through the gasification of cellulose-containing biomass whereas biogas is produced by anaerobic fermentation. Biomethane plants are currently in the demonstration stage. This fuel has the potential to be fed into existing natural gas networks. Plants in Gothenburg (Sweden) and Güssing (Austria) have plans to not only produce fuel, but also electricity and industrial goods. Another ZSW project is in the applied research stage; this project deals with the synthesis of methane from hydrogen-rich product gas that accumulates during the gasification of biomass in a process known as AER (absorption enhancing reforming). According to the ZSW, the product gas is of a quality that also makes it suitable for fuel production. Although the commercial implementation of the project (in the city of Geislingen) was long planned, it recently failed due to high biomass prices and the lack of energy purchasers. Research laboratories are experimenting with the use of algae for the production of biomethane.

BtL (biomass to liquid) fuels are produced from liquid biomass. They can be produced from virtually any type of biomass with a low percentage of moisture. The raw materials are gasified and purified; the synthesis gas is either produced and refined following the Fischer-Tropsch method or the methanol-to-gasoline method. Production methods are not yet competitive. The first large-scale pilot plant located in the Saxon city of Freiberg (Choren Industries) has recently declared bankruptcy; insiders (see blog on "Energycollective", listed in the "selected references" section) claim that the technology has been tested over a long period of time and functions well. The Karlsruhe KIT plans to finish construction of a pilot plant using the bioliq method sometime during 2012. Following the decentralised densification of energy (by way of rapid pyrolysis), the liquid biomass is gasified, purified, conditioned and refined in an entrained flow gasifier. The fuels produced are expected to be fit for use in different types of engines. In cooperation with five French partners and the technology provider Uhde (Thyssen-Krupp), the KIT plans to commence operating the two pilot plants for the production of biodiesel and biokerosene in the course of 2012.

Cellulosic ethanol, a 2G bioethanol, is chemically equivalent to its predecessor, but in contrast to the earlier version, it is produced from plant residues and waste products that have to be cleaved by acids and enzymes (which are still very expensive) before it can be fermented, distilled and purified. Since the 1970s, researchers have been focusing on the efficient and rapid processing of lignocellulose, which is more complex than cellulose, but a breakthrough is highly unlikely in the near future.

Ambitious 2G ethanol production targets such as the US government targets have recently been revised downwards (Biello, p. 61). Several 2G ethanol production demonstration plants are currently being established in Germany. The company Südchemie plans to produce up to 2000 t/y ethanol (ethanol cuts CO₂ emissions by 90 per cent) from lignocellulose (straw collected in the vicinity of the plant) from 2012 onwards in its plant in the Bavarian city of Straubing. The company sees itself as a technology provider that uses a decentralised approach. It envisages the establishment of economically feasible plants with an ethanol production capacity of 50 to 150 t per year. In addition to its demonstration plant, Südchemie also envisages the development of a larger-scale plant whose four-step process will be able to produce more than 1 t ethanol from 5 t cellulose using proprietary enzymes and C5 and C6 sugars.

In addition to the aforementioned, some pilot plants use thermochemical and biochemical methods to produce bioethanol from municipal (e.g. Enerkem, Montreal) and commercial waste. Laboratory-scale synthesis gas fermentation plants and plants for the gasification and synthesis of ethanol from lignocellulose are currently being developed.

A method that involves the hydration of plant oils and fats has been developed over the last few years. Fuel produced in this way is referred to as renewable diesel in order to differentiate it from esterified biodiesel. Neste Oil from Finland, the worldwide leader in renewable diesel, has recently established its fourth production facility in Rotterdam (NL), enabling it to increase its production capacity to two million t of renewable diesel per year. The company claims that this type of fuel is also suitable for aircraft.

Biogenic 2G fuels are of great interest for the aviation industry for two reasons: from 2012 onwards, the aviation industry will also be included in the EU-ETS trading system and will save money when using biofuel. At present, this is the only climate-saving alternative for the aviation industry. Initial approaches for the production of fuel from jatropha, false flax and household waste have been presented. In the long term, liquid (bio)methane and liquid hydrogen are regarded as ecologically sustainable alternatives to kerosene (dena, p. 30).

Biobutanol can be produced by way of the anaerobic microbial fermentation of carbohydrates and converting them into acetin, butanol and ethanol, but is unable to compete with the petrochemical production of butanol. Interest is growing in biobutanol fuel for use in Otto and diesel engines. The energy-rich alcohol, which is able to use the petrochemical infrastructure, can be produced from corn, sugarcane and sugarbeet as well as from raw materials that contain cellulose.

Experts see biobutanol as a better alternative to fossil fuel than bioethanol. New biobutanol production methods are being developed in order to produce biobutanol on an industrial scale. DuPont, BP and Gevo are planning to produce biobutanol from a broad range of different raw materials and BP and DuPont plan to commercialise biobutanol production by 2013.

Algae have provided high-quality products (cosmetics, chemicals, additions to food and feedstuff) to a small market for quite some time. However, the sustainability debate relating to 1G fuels has been stimulating interest in the use of micro- and macroalgae for the production of fuel. Is this a case of déjà vu? Back in the 1990s, the USA and Japan had already initiated funding programmes for the use of algae in the production of biofuel, which were then abandoned.

The mineral oil, chemical and cosmetics industries are currently testing the suitability of algae for the production of fuel (often referred to as third-generation (3G) fuel. However, this is still a costly process. Critics (e.g. Gerd Klöck) have come up with calculations to prove the negative energy balance of using algae for the production of fuel. Many people see a solution in the use of co-generated products (fats, proteins for industrial and material purposes, for the production of human food and animal feed).

The production of algal fuel requires large areas of cultivation; European transport would require an area the size of Portugal if it were to use algal fuel to cover all its fuel requirements - at least in theory. Using synthetic biology tools, researchers are working on the integration of individual genes as well as entire metabolic pathways into photographic microorganisms in order to create new cell systems for the production of biofuel. The dream of green foam will still be just a dream for some time to come.

Selected references:

AIREG (Aviation Initiative for Renewable Energy in Germany), 8th June 2011 (www.airliners.de)

Asendorpf, Dirk: Unsere Gier nach Futter, Die Zeit, 19th December 2011.

Biello, David: The False Promise of Biofuels, Scientific American, August 2011, p. 59ff.

Biofuels Digest: https://www.biooekonomie-bw.dewww.biofuelsdigest.com

Bley, Thomas (Ed.): Biotechnologische Energieumwandlung, Berlin Heidelberg 2009.

Deutsche Energie-Agentur (dena; German Energy Agency) (Ed.): Entwicklung einer Mobilitäts- und Kraftstoffstrategie für Deutschland. Voruntersuchung, Berlin August 2011.

Dr. John Benemann's Take on the Current State of the Algae Industry, Algaenews.com, 9.12.2011.

Fairley, Peter, Next Generation Biofuels, Nature 474, 23rd June 2011 (doi:10.1038/474S02a)

Hurtig, Oliver, Leible, Ludwig et al., ITAS (Institut für Technikfolgenabschätzung und Systemanalyse): Die Automobilindustrie auf neuen Wegen? Eine vergleichende Einordnung innovativer Kraftstoff- und Antriebskonzepte der deutschen Automobilindustrie seit der ersten Ölkrise 1973, in: Technikfolgenabschätzung – Theorie und Praxis, 19/3, December 2010, p. 84ff.

Kevin Bullis: To Survive, Some Biofuels Companies Give Up on Biofuels, Technology Review, 21st December 2011

Klöck, Gerd: It’s the Process, Stupid, Chemistry & Industry, 22nd February 2010, p. 27.

Kruse, Olaf: Synthetische Biologie und Biotreibstoffe, in: Alfred Pühler/Bernd Müller-Röber/Marc-Denis Weitze (Ed.):  Synthetische Biologie. Die Geburt einer neuen Technikwissenschaft. (acatech Diskussion), Munich 2011, p. 95ff.

Südchemie: Sunliquid, Nature’s Quality in Fuel; presentation by Dr. Ulrich Kettling at BIOTECHNICA, Hanover, Germany, 12th October 2011.

SWAFEA (Sustainable Way for Alternative Fuel and Energy in Aviation), State of the Art for Alternative Fuels and Energy Carriers in Aviation, AFEA formal report D.2.1 v2 (WP2000_USFD_25/03/2010), 1st October 2011

What Happened at Choren: https://www.biooekonomie-bw.detheenergycollective.com/robertrapier/60963/what-happened-choren, posted 9th July 2011.