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    Mongabay, a leading resource for news and perspectives on environmental and conservation issues related to the tropics, has launched Tropical Conservation Science - a new, open access academic e-journal. It will cover a wide variety of scientific and social studies on tropical ecosystems, their biodiversity and the threats posed to them. Tropical Conservation Science - March 8, 2008.

    At the 148th Meeting of the OPEC Conference, the oil exporting cartel decided to leave its production level unchanged, sending crude prices spiralling to new records (above $104). OPEC "observed that the market is well-supplied, with current commercial oil stocks standing above their five-year average. The Conference further noted, with concern, that the current price environment does not reflect market fundamentals, as crude oil prices are being strongly influenced by the weakness in the US dollar, rising inflation and significant flow of funds into the commodities market." OPEC - March 5, 2008.

    Kyushu University (Japan) is establishing what it says will be the world’s first graduate program in hydrogen energy technologies. The new master’s program for hydrogen engineering is to be offered at the university’s new Ito campus in Fukuoka Prefecture. Lectures will cover such topics as hydrogen energy and developing the fuel cells needed to convert hydrogen into heat or electricity. Of all the renewable pathways to produce hydrogen, bio-hydrogen based on the gasification of biomass is by far both the most efficient, cost-effective and cleanest. Fuel Cell Works - March 3, 2008.

    An entrepreneur in Ivory Coast has developed a project to establish a network of Miscanthus giganteus farms aimed at producing biomass for use in power generation. In a first phase, the goal is to grow the crop on 200 hectares, after which expansion will start. The project is in an advanced stage, but the entrepreneur still seeks partners and investors. The plantation is to be located in an agro-ecological zone qualified as highly suitable for the grass species. Contact us - March 3, 2008.

    A 7.1MW biomass power plant to be built on the Haiwaiian island of Kaua‘i has received approval from the local Planning Commission. The plant, owned and operated by Green Energy Hawaii, will use albizia trees, a hardy species that grows in poor soil on rainfall alone. The renewable power plant will meet 10 percent of the island's energy needs. Kauai World - February 27, 2008.

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Tuesday, October 28, 2008

Interview: Axel Tarrisse makes biogas from drought-tolerant cacti

High energy prices and concerns about climate change have pushed a number of countries to invest in renewable energy. However, renewables have their drawbacks. Wind and solar are intermittent sources, and cost-effective energy storage options are not available yet, making these sources dependent on fossil fuel baseloads (previous post). Biomass power plants provide an excellent green alternative baseload, but not all countries have the necessary biomass resources. Drought-prone and semi-arid regions in particular would find it difficult to rely on energy crops. However, perhaps there is a solution: what if we could grow drought-tolerant crops on marginal land and convert them into biogas?

Axel Tarrisse with a 3 year old Opuntia.
For the past years, Axel Tarrisse has been researching the issue and found that Opuntia – a genus of spineless cacti – could be an excellent candidate for the job. Tarrisse made a case-study about the potential of the prickly plants in Turkey and found promising results. His previous research on drought-tolerant fodder crops and his worries about the rising costs of energy and fertilizers for farmers, allowed him to design a highly integrated biogas production concept in which nothing goes to waste. Biopact's Jonas Van Den Berg had a talk with the researcher. A powerpoint presentation of Tarrisse's research on Opuntia and biogas can be found here.

Biopact: How did you come to research Opuntia as a feedstock for biogas?
Axel Tarrisse: I have been concentrating my studies on the use of drought tolerant fodder shrubs for the rehabilitation of marginal lands. Then I discovered the use of maize silage as a feedstock for biogas production in Germany. The impressive yield of biomass obtained from spineless cacti could be used instead of maize silage in biogas production.

Using spineless cacti as an energy crop is offering serious perspectives to countries prone to drought and relying on imports for their energy consumption. Under a mediterranean climate, Opuntia can easily be cultivated under rain fed conditions without any supplementary irrigation, whereas maize cannot be cultivated without it.

Opuntia planted in March 2008 and growing well into July.
Biopact: What are the advantages of spineless cactus species as energy crops?
Tarrisse: Spineless cacti have a high water use efficiency, they can be grown with limited water on marginal lands, creating a valuable source of biomass on degraded land in semi-arid regions.

Biopact: Opuntia may be drought-tolerant, but do these cacti yield enough biomass?
Tarrisse: Opuntia ficus indica inermis respond very strongly to fertilization and irrigation. 100 tons of fresh biomass (12 t DM) /ha/year can be harvested with 300 mm of rainfall. 500 tons of fresh biomass/ha/year is obtained in Santiago de Chile and in the North East of Brazil where it is harvested just one year after planting under intensive cultivation.

Under the same irrigated and fertilized intensive culture Opuntia can yield around 120,000 kWh/ha/year, which is twice as much as maize under a mediterranean climate.

Micropropagated Opuntia.
Biopact: You wrote a case-study about the potential of Opuntia in Turkey. Can it replace a lot of natural gas?
Tarrisse: 4000 m3 of natural gas equivalent can be produced per hectare per year under rainfed conditions with an annual rainfall of 300-350 mm. Opuntia isn’t well known in Turkey, but 2 million hectares of marginal and low productive agricultural land is available for it. There's a potential for the creation of 200,000 to 300,000 new jobs, with an industry representing US$2 billion in economic value:
:: :: :: :: :: :: :: :: :: :: :: ::

North Africa and the North East of Brazil have 500,000 ha of Opuntia plantations each, South Africa has around 300,000 ha where the crop is used as a drought fodder.

Tunisia imports 2 billion m3 of natural gas annually, while the country already has 500,000 ha of spineless cactus plantations which could replace this entire amount of natural gas. This way it could save US$400 million on imports each year.

In the North East of Brazil 1,400,000 ha of Opuntia plantations under intensive cultivation would be enough to replace Brazil's entire annual 21 billion m3 of natural gas consumption, which corresponds to US$4.2 billion.

Biopact: Can the cultivation of the cacti be integrated in existing cropping systems?
Tarrisse: Yes indeed. The integration of Opuntia into existing cultivated areas can be done in strips (strip-cropping). That way existing cultures are not replaced by the cacti, but supported by this culture as the residue from biogas production would be returned to the soil as an organic fertilizer.

Biopact: How about the economics? Would Opuntia-biogas be competitive with natural gas at current prices?
Tarrisse: I estimate the total cost of producing biogas from Opuntia in Turkey — including the investment, the running cost, and the biomass — at €25/MWh of gas produced. The price of natural gas in September 2008 in Turkey was €39/MWh. In short, Opuntia-biogas would be competitive. This is mainly due to the fact that he cost of the biomass feedstock alone is around €10/MWh of gas, which is definitely lower per unit of energy produced than other dedicated energy crops used as a feedstock for anaerobic digestion. The income generated by the production of organic fertilizer shouldn’t be overlooked either, as it covers the cost of biomass production.

Vermicompost made from digestate from Opuntia.
Biopact: It seems like your research could provide a base for projects in developing countries, in particular in semi-arid regions. Are any projects being planned? Have you had feedback from potential investors?
Tarrisse: I have planned the possible implementation of a bioenergy park for the organized industrial zone of Adana in the South of Turkey.

The French and Turkish investors I have met so far were mainly interested in electricity generation. The guaranteed price of €0.05/kWh for electricity isn’t enough for the economic viability of the project if electricity is the only output to be sold. Work should be done on legislation promoting the injection of biomethane into the natural gas network, as it has been done in Turkey for biodiesel and bioethanol, or in Germany for biogas.

It is important for investors to take a multidisciplinary approach to the project, taking into account the value of the other outputs: organic fertilizers and heat recovery (steam, hot water) when electric generation is intended. If seen as an integrated concept, Opuntia-biogas production can offer both a competitive and sustainable source of renewable energy.

Axel Tarrisse was born in 1985 in Montpellier France, spent his childhood in Istanbul, attending primary and secondary schools at the Lycee Français d’Istanbul and later studied Geography land management and Rural Resources Management at the Lyon III University in France and at the Hohenheim University in Germany. He focuses his work on the efficiency of farming systems and development issues in semi-arid areas. Axel can be contacted at .

Slideshow: all pictures reproduced with kind permission from Henri Noel Le Houérou.

Pictures in text, credit: Axel Tarrisse 2008.

Tarrisse, A. “Biogas from Opuntia: A Source of Renewable Gas and Fertilizer” - powerpoint presentation, October 2008.

Tarrisse, A. Natural gas consumption of Turkey and the strategic use of drought tolerant energy crops for biogas production, Thesis, ESE-IER-Lyon III University - September 2008.


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