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Tag Archives: bioenergy

Biomass limits (Part 2)

Liquid biofuels for transport, but also other types of biomass production and use, have been promoted as away to reduce greenhouse gas emissions, boost rural development and ensure energy independence. However this approach has run up against major constraints, including land-use and biodiversity issues. Moving to second generation non-food biofuels, and also biomass wastes, may help, as may tighter regulation (see my previous Blog http://environmentalresearchweb.org/blog/2011/09/biomass-limits–1.html

But there may also be clever approaches that avoid some of the land-use limits of biomass.

Perhaps the most obvious is to use biomass differently. Biogas production via anaerobic digestion (AD), e.g. of bio wastes, is widely seen as a good idea – coupled with using the gas grid for delivery. You can then use it for heating. But you can also use biogas in car engines. For example, it’s been claimed that methane through AD requires only about a quarter of the land area ethanol requires, and is a far more efficient fuel than ethanol, easily used in cars and trucks. There are certainly enthusiasts for it in the UK and elsewhere: http://news.mongabay.com/bioenergy/2007/12/biomethane-presented-as-most-efficient.html
and [www.biogaspartner.de/index.php?id=11229&L=1&fs=0\\%27%3Fiframe%3Dtrue
](http://www.biogaspartner.de/index.php?id=11229&L=1&fs=0\\%27%3Fiframe%3Dtrue)

Another option is to produce hydrogen by thermo-chemical processing of biomass/wastes, as proposed by Karl-Heinz Tetzlaff, possibly combined with CCS.
www.claverton-energy.com/wp-content/uploads/2010/07/Tetzlaff_Birmingham2010.pdf

The hydrogen can be used for heating, possibly admixed with methane and delivered via the gas main; in fuels cells; or as a vehicle fuel direct. Or it can be used to make syngas /ammonia.

There are however some efficiency penalties involved with these various conversions. A PhD thesis by Anna Suess from Eindhoven Technical University looks at biomass as a CO2 saving technology. She compared synthetic natural gas (SNG), methanol, Fischer-Tropsch fuels, hydrogen and bioelectricity. Although she concludes that the overall practical resource is limited, the best option evidently proved to be converting biomass into electricity and using that to power electric cars. ‘First of all, biomass can be converted efficiently into electricity. Electricity can also be generated in smaller plants, which reduces the need for transport. And finally, electricity is a clean and efficient energy source for vehicles’. That certainly fits with the current vogue for an all-electric green energy future with cars run of electricity from renewable sources, but whether bio-conversion is better than electrolysis (e.g. using wind generated electricity) is far from clear- although you can store biomass. http://w3.tue.nl/en/news/news_article/?tx_ttnewstt_news=10544&tx_ttnewsbackPid=926&cHash=5464e54533(http://w3.tue.nl/en/news/news_article?/tx_ttnewstt_news=10544&tx_ttnewsbackPid

However there are also more radical approaches. For example , “Breaking the Biomass Bottleneck”, a report by Henrik Wenzel (from Concito, a green ‘think tank’ in Denmark), suggest that we could upgrade biomass by hydrogenation, using hydrogen produced by the electrolysis of water, powered by excess electricity from variable renewables like wind. The report claims that you can react biomass with hydrogen ‘to produce hydrocarbons of much higher energy content and energy density than the original biomass. Moreover, using the biomass and the biogenic carbon from hydrogenation in central applications like heat and power , it is possible to collect the CO2 from the biomass and further recover and recycle it in a process here called Carbon Capture and Recycling, CCR. This will further multiply the use of the biogenic carbon from the biomass. Overall, upgrading and recycling biogenic carbon by hydrogenation and CCR, can approximately five-double our biomass potential for providing storable and high-density fuels and carbon feedstock compared to the presently applied technologies for converting biomass to fuels and feedstock.’

This sound wonderful- something for nothing, although, not really, since it can’t invalidate the laws of thermodynamics. But, the report notes, even with electrolysis losses, 1 Joule of wind can save 1 Joule of biomass, by upgrading it. However, the report adds ‘The total energy content of the biomass and the hydrogen is, of course, greater than that of the fuels on the output side. If, therefore, hydrogen is sufficiently good for the demanded energy services in question, there is no sense in taking a detour of producing the carbon based fuels from the hydrogen. The conversion from hydrogen to carbon fuels as energy carrier is only justified by the inherent differences in the properties and qualities of the two’.

So it’s end-use utility that matters, especially as it costs more, given the efficiency loses. But even so, the report claims that it makes sense. Not only go you get a valuable green fuel, you can also store it easily and help balance variable wind and other renewables, while using less biomass and less land. Moreover, if the biomass used is replaced consistently and sustainably, and you capture the CO2 produced when the fuel is burnt, then you have an overall net carbon negative system- although the report says that transport uses are less attractive, since then you can’t capture the CO2. www.concito.info/en/udgivelser.php

There are also versions of this idea which just use hydrogen produced from wind derived electricity and carbon dioxide from the atmosphere, to generate methane, methanol or some other synfuel. See for example www.airfuelsynthesis.com

It would in effect create a carbon neutral fuel from the movement of and COs in the air, and it could be carbon negative if the CO2 was collected after combustion. Moreover, it avoids biomass land-use issues entirely. However air capture of CO2 still remains very expensive, so biomass looks a more likely carbon feedstock for the moment.

All in all though, there’s some clever green chemistry emerging. For more see: www.iset.uni-kassel.de/abt/FB-I/publication/2010-088_Towards-renewables.pdf]

Another very ambitious approach involves using algae, or other biomass, grown in desert areas, possibly coupled with CCS. It’s been argued that, if algae is grown at the yields that the IEA Task Force bio-energy says is credible, then a land area the size of 24 % of Australia (in practice spread around Earth’s deserts) would produce 90,000 TWh/y which nearly equivalent to the current global final energy demand of 98,000 TWh/y. Moreover if some of that algae /biomass is used in CCS schemes then we would have a powerful carbon-negative energy technology: BECCS – bio-energy with CCS.

The Global CCS Institute has just produced a report which concludes: ‘there is a widespread unawareness of BECCS amongst policy makers, and also a lack of research and demonstration programs directed at the BECCS segment of climate mitigation measures. The insufficient efforts in research and deployment of BECCS are detrimental not only for the biomass industries, but for climate mitigation policies in general. Studies show that billions and trillions of Euros could be saved by including BECCS in mitigation portfolios. There are also large benefits to be gained in developing joint transportation and storage systems for fossil fuel CCS and BECCS, as this would increase economies of scale and lower the costs’. www.globalccsinstitute.com/resources/publications/global-status-beccs-projects-2010

One way to do this might be by growing algae in a Seawater Greenhouse www.seawatergreenhouse.com(http://www.seawatergreenhouse.com) As I’ve noted before, the first commercial SG scheme is up and running in Australia and more are planned around the world, possibly in conjunction with CSP technologies, to desalinate water. See www.sundropfarms.com.au/

For food or algae production, as well as energy and water, you have to provide nutrients. One way to do this might be to stir up the sea-bed near the water entry point and suck in the sediment, then filter and dry it. Of course there are many uncertainties in relation to, for example, costs and impacts on fragile desert and marine ecosystems. However, the Dutch routinely use ocean sediment, allowing the saline content to drain back to the sea. Clearly, if this is to be done on any scale, we will need some detailed Life Cycle Assessments first.
See http://sinig.net/e19.pdf

Certainly many ‘greens’ are worried about the use of biofuels to keep the cars (and planes) going for a range of reasons.. See for example:
www.theecologist.org/News/news_analysis/852075/germany_joins_up_with_lufthansa_to_sponsor_biofuel_six_times_worse_than_fossil_fuels.html
and www.theecologist.org/News/news_round_up/745752/biofuels_jatropha_still_linked_to_land_grabbing_and_displacement_of_farmers.html

Moreover, in terms of electricity and heat production, many would see conventional flow renewables, like solar, wind, wave and tidal power, as a better bet, with fewer eco impacts: e.g. see Mark Delucchi’s biomass LCA studies: Ann. N.Y. Acad. Sci. 1195 (2010) 28-45 and Biomass and Bioenergy (2010), doi:10.1016/j.biombioe.2010.11.028

The debate continues, with the latest input being a fairly critical report from the RSPB: ‘Bioenergy: A Burning Issue’, which says the rush to build new power stations in the UK will mean that imports of the wood needed will have to rise from 13% to 68%- three times higher than the UK’s total current wood production. [www.rspb.org.uk/news/288724-study-exposes-green-failings-of-wood-fuel-power-plans-.
](http://www.rspb.org.uk/news/288724-study-exposes-green-failings-of-wood-fuel-power-plants-)

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