A general view shows the new waste collection plant which creates what is known as Refuse Derived Fuel (RDF) in the outskirts of Tel Aviv, Israel March 26, 2017. Picture taken March 26, 2017. REUTERS/Nir Elias

Mohammad Zayed carries a bucket of waste to be used in a HomeBioGas portable reactor that turns food leftovers and manure into methane outside his home in the Palestinian Bedouin village of Ojah, near the West Bank city of Jericho August 17, 2015. Palestinian villagers living in desolate, off-grid areas in the West Bank have begun using Israeli-made biogas generators that supply free, clean energy by gobbling up organic waste. Picture taken August 17, 2015. REUTERS/Ammar Awad

Mohammad Zayed fills a bucket with waste to be used in a HomeBioGas portable reactor that turns food leftovers and manure into methane outside his home in the Palestinian Bedouin village of Ojah, near the West Bank city of Jericho August 17, 2015. Palestinian villagers living in desolate, off-grid areas in the West Bank have begun using Israeli-made biogas generators that supply free, clean energy by gobbling up organic waste. Picture taken August 17, 2015. REUTERS/Ammar Awad

Nayef Zayed lights a gas burner running on methane produced in a HomeBioGas portable reactor in his home in the Palestinian Bedouin village of Ojah, near the West Bank city of Jericho August 17, 2015. Palestinian villagers living in desolate, off-grid areas in the West Bank have begun using Israeli-made biogas generators that supply free, clean energy by gobbling up organic waste. Picture taken August 17, 2015. REUTERS/Ammar Awad

Nayef Zayed and his son Mohammad prepare to pour waste into a HomeBioGas portable reactor that turns food leftovers and manure into methane outside their home in the Palestinian Bedouin village of Ojah, near the West Bank city of Jericho August 17, 2015. Palestinian villagers living in desolate, off-grid areas in the West Bank have begun using Israeli-made biogas generators that supply free, clean energy by gobbling up organic waste. Picture taken August 17, 2015. REUTERS/Ammar Awad

Nayef Zayed empties a bucket of waste into a HomeBioGas portable reactor that turns food leftovers and manure into methane outside his home in the Palestinian Bedouin village of Ojah, near the West Bank city of Jericho August 17, 2015. Palestinian villagers living in desolate, off-grid areas in the West Bank have begun using Israeli-made biogas generators that supply free, clean energy by gobbling up organic waste. Picture taken August 17, 2015. REUTERS/Ammar Awad

Nayef Zayed empties a bucket of waste into a HomeBioGas portable reactor that turns food leftovers and manure into methane outside his home in the Palestinian Bedouin village of Ojah, near the West Bank city of Jericho August 17, 2015. Palestinian villagers living in desolate, off-grid areas in the West Bank have begun using Israeli-made biogas generators that supply free, clean energy by gobbling up organic waste. Picture taken August 17, 2015. REUTERS/Ammar Awad

Sons of Nayef Zayed stand next to a Home Biogas portable reactor that turns food leftovers and manure to make methane, outside their home in the Palestinian Bedouin village of Ojah, near the West Bank city of Jericho August 17, 2015. Palestinian villagers living in desolate, off-grid areas in the West Bank have begun using Israeli-made biogas generators that supply free, clean energy by gobbling up organic waste. Picture taken August 17, 2015. REUTERS/Ammar Awad

A woman walks through a field with bio-diesel in the north-eastern Greek region of Thrace near the town of Xanthi April 18, 2014. In the mid 80s Greece produced 400,000 tons of sunflower yearly, in 2005 this crop nearly disappeared. Therefore, the biofuel production presented as an opportunity to exploit 1,000,000 acres of uncultivated Greek land. From almost zero production in 2011 more than 1,000,000 acres of energy crops were cultivated attributing to the Greek countryside people more than 100.000.000 euros yearly. REUTERS/Yannis Behrakis (GREECE - Tags: BUSINESS ENERGY ENVIRONMENT)

Stephan Martinez, owner of Le Petit Choiseuil bistrot, poses next to food waste garbage in the kitchen of his restaurant in Paris February 12, 2014. A group of Paris restaurants is turning food scraps into biogas and compost ahead of a new law that will force thousands of French food outlets to recycle their organic waste. Some 80 restaurants, caterers and hotels, signed up for a pilot project to collect their food waste, which is used to generate biogas and produce electricity and heat, as well as compost for farms around Paris. Martinez, who took the initiative for the project, said the collection anticipates the law but that participating restaurants are happy that someone collects their waste and puts it to good use. REUTERS/Charles Platiau (FRANCE - Tags: FOOD ENVIRONMENT SOCIETY ENERGY)

Algae grown in a special water system is seen at Israeli biofuel firm, Univerve's demonstration site at Bar-Ilan University, near Tel Aviv December 15, 2013. Israel plans to cut oil use in transportation by 60 percent by 2025, an aggressive target by world standards, and will tap into its newfound natural gas deposits to make it happen. It is also investing heavily to help start-ups developing battery and biofuel technologies. Picture taken December 15, 2013. REUTERS/Nir Elias (ISRAEL - Tags: ENERGY ENVIRONMENT)

A picture shows a biomass silo and a wind turbine that contribute energy to a hybrid power plant near the town of Schenkenberg north of Berlin, February 29, 2012. Vattenfall partnered up with renewable energy firm Enertrag for a pilot project in emission free mobility, powering cars with hydrogen that is produced by a CO2-neutral hybrid power plant. To go with feature GERMANY-POWER/HYDROGEN REUTERS/Thomas Peter (GERMANY)

A woman pastes cow dung cakes on a wall, used as cooking fuel, on the outskirts of Lahore on February 2, 2012. REUTERS/Mohsin Raza (PAKISTAN - Tags: SOCIETY ENVIRONMENT)

A girl covers cow dung patties with hay to store them for cooking fuel in the outskirts of Lahore on November 15, 2011. REUTERS/Mohsin Raza (PAKISTAN - Tags: SOCIETY POVERTY ENVIRONMENT)

A view of what the Curitiba City Hall is calling the world's longest articulated bus, as it was presented to the press before going into service on the city's public transportation grid, in Curitiba April 5, 2011. The bus, made in Brazil by Volvo with a Neobus chassis, has a capacity of 250 passengers, is 28 meters (92 ft) long, 2.6 meters (8.5 ft) wide, and powered with biodiesel made from soybeans. REUTERS/Rodolfo Buhrer (BRAZIL - Tags: ENERGY TRANSPORT ODDLY)

A view of what the Curitiba City Hall is calling the world's longest articulated bus, as it was presented to the press before going into service on the city's public transportation grid, in Curitiba April 5, 2011. The bus, made in Brazil by Volvo with a Neobus chassis, has a capacity of 250 passengers, is 28 meters (92 ft) long, 2.6 meters (8.5 ft) wide, and powered with biodiesel made from soybeans. REUTERS/Rodolfo Buhrer (BRAZIL - Tags: ENERGY TRANSPORT ODDLY IMAGES OF THE DAY)

Jatropha seeds, the oil of which is used to produce biofuel, are seen in Chiapas April 1, 2011. An Interjet Airlines Airbus 320 passenger plane using biofuel landed at Angel Albino Corzo of Tuxtla Gutierrez airport in Chiapas on Friday. The flight, from Mexico City's International Airport, was the first in Mexico partially powered (27%) by biofuel, the Mexican airport authority Aeropuertos y Servicios Auxiliares (ASA) said. REUTERS/Henry Romero (MEXICO - Tags: TRANSPORT ENERGY)

A chemical engineer places a hand on a pipe filled biofuel at Oleoplan factory in Passo Fundo, 300 km (186 miles) southwest of Porto Alegre, May 21, 2010. With its biofuels business increasingly dominated by giant corporations, Brazil is seeking to extend the sector to include small farmers who can improve their incomes by planting the crops used to make fuel. Picture taken May 21. To match Feature BRAZIL-BIOFUELS/ REUTERS/Bruno Domingos (BRAZIL - Tags: BUSINESS ENERGY) )

Containers of different kinds of seeds are seen at Oleoplan factory in Passo Fundo, 300 km (186 miles) southwest of Porto Alegre, May 21, 2010. With its biofuels business increasingly dominated by giant corporations, Brazil is seeking to extend the sector to include small farmers who can improve their incomes by planting the crops used to make fuel. Picture taken May 21. To match Feature BRAZIL-BIOFUELS/ REUTERS/Bruno Domingos (BRAZIL - Tags: BUSINESS ENERGY SCI TECH)

A chemical engineer checks a flask of biofuel at Oleoplan factory in Passo Fundo, 300 km (186 miles) southwest of Porto Alegre, May 21, 2010. With its biofuels business increasingly dominated by giant corporations, Brazil is seeking to extend the sector to include small farmers who can improve their incomes by planting the crops used to make fuel. Picture taken May 21. To match Feature BRAZIL-BIOFUELS/ REUTERS/Bruno Domingos (BRAZIL - Tags: BUSINESS ENERGY SCI TECH)

A chemical engineer holds up a test-tube of biofuel at Oleoplan factory in Passo Fundo, 300 km (186 miles) southwest of Porto Alegre, May 21, 2010. With its biofuels business increasingly dominated by giant corporations, Brazil is seeking to extend the sector to include small farmers who can improve their incomes by planting the crops used to make fuel. Picture taken May 21. To match Feature BRAZIL-BIOFUELS/ REUTERS/Bruno Domingos (BRAZIL - Tags: BUSINESS ENERGY SCI TECH AGRICULTURE)

A man checks canola seeds at Oleoplan factory in Passo Fundo, 300 km (186 miles) southwest of Porto Alegre, May 21, 2010. With its biofuels business increasingly dominated by giant corporations, Brazil is seeking to extend the sector to include small farmers who can improve their incomes by planting the crops used to make fuel. Picture taken May 21. To match Feature BRAZIL-BIOFUELS/ REUTERS/Bruno Domingos (BRAZIL - Tags: BUSINESS ENERGY AGRICULTURE)

A worker walks through a trash dump in Makassar in Indonesia's South Sulawesi province June 7, 2010. An Indonesian company has been producing methane gas from the 400-500 tons of trash dumped daily in this area and plans to supply the gas for electricity needs. REUTERS/Yusuf Ahmad (INDONESIA - Tags: ENVIRONMENT)

A worker of green energy producer 4Energy Invest looks at biomass at Renogen plant in Amel April 2, 2010. Belgian bio-coal maker 4Energy Invest expects earnings to rise 10 percent in the second half of 2010, and sees sales up tenfold within four years on a surge in demand for the CO2-neutral fuel. To match interview 4ENERGY/ REUTERS/Thierry Roge (BELGIUM - Tags: ENVIRONMENT BUSINESS)

Biodiesel is pumped into a car at the Sime Darby Biodiesel Plant in Carey Island, outside Kuala Lumpur, March 24, 2010. Malaysia will roll out its biodiesel mandate in phases beginning June 2011, commodities minister Bernard Dompok said. REUTERS/Bazuki Muhammad (MALAYSIA - Tags: ENVIRONMENT BUSINESS ENERGY TRANSPORT)

General view of the Patagonia Bioenergia biodiesel plant in San Lorenzo February 26, 2010. Argentina is set to implement a law requiring diesel to be blended with biodiesel in the coming weeks, but the nation's key exports of the green fuel could still rise as production soars. Argentina, a leading exporter of biodiesel and the No. 1 soyoil supplier, was due to introduce the law on Jan. 1, but it was delayed until the government agreed to allocate supply quotas to the country's top producers, industry sources say. Picture taken February 26, 2010. To match analysis ARGENTINA-BIODIESEL/ REUTERS/Enrique Marcarian (ARGENTINA - Tags: POLITICS ENERGY ENVIRONMENT)

Biodiesel is seen through a tube at Patagonia Bioenergia biodiesel refinery in San Lorenzo February 26, 2010. Argentina is set to implement a law requiring diesel to be blended with biodiesel in the coming weeks, but the nation's key exports of the green fuel could still rise as production soars. Argentina, a leading exporter of biodiesel and the No. 1 soyoil supplier, was due to introduce the law on Jan. 1, but it was delayed until the government agreed to allocate supply quotas to the country's top producers, industry sources say. Picture taken February 26, 2010. To match analysis ARGENTINA-BIODIESEL/ REUTERS/Enrique Marcarian (ARGENTINA - Tags: POLITICS ENERGY ENVIRONMENT)

A worker goes down by a Patagonia Bioenergia biodiesel plant in San Lorenzo February 26, 2010. Argentina is set to implement a law requiring diesel to be blended with biodiesel in the coming weeks, but the nation's key exports of the green fuel could still rise as production soars. Argentina, a leading exporter of biodiesel and the No. 1 soyoil supplier, was due to introduce the law on Jan. 1, but it was delayed until the government agreed to allocate supply quotas to the country's top producers, industry sources say. Picture taken February 26, 2010. To match analysis ARGENTINA-BIODIESEL/ REUTERS/Enrique Marcarian (ARGENTINA - Tags: POLITICS ENERGY ENVIRONMENT)

A formula 3 race car that researchers from the University of Warwick in Britain have retrofitted is seen at the MIT Energy Conference 2010 in Boston, Massachusetts March 5, 2010. Fueled by leftover chocolate and with components made from carrots, potato starch and flax, the world's first sustainable Formula 3 racing car has a top speed of 135 miles per hour and can go from zero to 60 in 2.5 seconds. Picture taken March 5, 2010. To match Reuters Life! CAR-CHOCOLATE. REUTERS/Adam Hunger (UNITED STATES - Tags: SPORT MOTOR RACING ENVIRONMENT)

Sugar cane is seen near Santa Lucia Cotzumalguapa, Guatemala February 10, 2010. Guatemala exported 140,319 tonnes of sugar in January, down 23.8 percent from the same month last year, the country's sugar producers association Asazgua told Reuters on Wednesday. Picture taken February 10, 2010. REUTERS/Daniel LeClair (GUATEMALA - Tags: BUSINESS)

BIOFUEL-ETHANOL/ - 3D diagram showing ethanol production process. Previously transmitted on 06/05/2008

BIOFUEL-ETHANOL/ - 3D diagram showing ethanol production process. Previously transmitted on 06/05/2008

A Colombian engineer explains the process of oil palm extraction in a laboratory in Villanueva Casanare province, August 21, 2009. Colombia's palm oil industry will focus on the local market over the years ahead, taking advantage of a national biodiesel development program. Picture taken on August 21, 2009. REUTERS/Nelson Bocanegra (COLOMBIA SOCIETY ENVIRONMENT ENERGY BUSINESS)

Biomass, the unused portions of logged trees such a branches and the tree tops, sit at the Old Town Fuel and Fiber mill to be burned to generate electricity in Old Town, Maine, June 2, 2009. Old Town Fuel and Fiber opened in the spring in the former Old Town pulp and paper mill, which shut down three years ago, with a focus on biofuels as well as traditional logging. REUTERS/Brian Snyder (UNITED STATES)

Wood chips are stored in preparation for being turned into paper pulp at the Old Town Fuel and Fiber mill in Old Town, Maine, June 2, 2009. Old Town Fuel and Fiber opened in the spring in the former Old Town pulp and paper mill, which shut down three years ago, with a focus on biofuels as well as traditional logging. Picture taken June 2, 2009. To match feature USA-FORESTRY/BIOFUEL REUTERS/Brian Snyder (UNITED STATES BUSINESS ENERGY)

Steam emits out of the EnerTech Rialto Regional Biosolids Processing Facility in Rialto, California June 11, 2009. EnerTech Environmental, an Atlanta startup, on Thursday unveiled the United States' first commercial biosolids-to-energy facility in California's Inland Empire. "Biosolids" is the nice term for processed sewage sludge. To match Interview ENERTECH/ REUTERS/Nichola Groom (UNITED STATES ENERGY BUSINESS ENVIRONMENT)

A vial of EnerTech eFuel biosolid is shown in this photo taken June 11, 2009. EnerTech Environmental, an Atlanta startup, on Thursday unveiled the United States' first commercial biosolids-to-energy facility in California's Inland Empire. "Biosolids" is the nice term for processed sewage sludge. To match Interview ENERTECH/ REUTERS/Sam Mircovich (UNITED STATES ENERGY ENVIRONMENT BUSINESS)

Engineers stand near the new ethanol factory during its inauguration by Sudan's President Omar Hassan al-Bashir at the Kenana sugar factory in White Nile State June 10, 2009. REUTERS/Mohamed Nureldin Abdallh (SUDAN ENERGY BUSINESS)

A wind turbine is pictured in a field of miscanthus, or "Elephant Grass", at Renewables Energy Systems' green technology and renewable energy site at Kings Langley in southeast England April 23, 2009. Miscanthus is a biomass energy crop and is burned as a fuel in a biomass boiler to provide heat to the site. REUTERS/Luke MacGregor (BRITAIN ENVIRONMENT ENERGY)

An ethanol E10 fuel pump is seen at a petrol station in Pierrelaye, near Paris, April 15, 2009. REUTERS/Charles Platiau (FRANCE POLITICS ENERGY TRANSPORT)

Rachel Farnelli rides on her backyard swing that overlooks the Gesford #3 natural gas well in Dimock, Pennsylvania, March 7, 2009. Dimock is one of hundreds of sites in Pennsylvania where energy companies are now racing to tap the massive Marcellus Shale natural gas formation. But some residents say the drilling has clouded their drinking water, sickened people and animals and made their wells flammable. Picture taken March 7, 2009. To match feature ENERGY-GAS/TOWN REUTERS/Tim Shaffer (UNITED STATES ENERGY ENVIRONMENT SOCIETY)

Samples of Biodiesel (L) and Jatropha oil are seen at a processing plant outside Guatemala City March 5, 2009. All his life elderly Mexican farmer Gonzalo Cardenas has planted a stalky weed that grows wild in southern Mexico to form a sturdy live fence around his tropical fruit trees. It turns out the weed, jatropha, could be used to fuel jet planes and the Mexican government wants farmers to grow entire fields of it to turn into biodiesel. Picture taken March 5, 2009. To match feature MEXICO-BIOFUEL/ REUTERS/Daniel LeClair (GUATEMALA ENERGY)

A researcher checks samples of the toxic Jatropha fruit, or 'Pinon' at a research facility in Rosario Izapa February 26, 2009. All his life elderly Mexican farmer Gonzalo Cardenas has planted a stalky weed that grows wild in southern Mexico to form a sturdy live fence around his tropical fruit trees. It turns out the weed, jatropha, could be used to fuel jet planes and the Mexican government wants farmers to grow entire fields of it to turn into biodiesel. Picture taken February 26, 2009. To match feature MEXICO-BIOFUEL/ REUTERS/Daniel LeClair (MEXICO ENERGY)

A worker at Biocombustibles, a Guatemalan company producing biodiesel from a non-edible plant jatropha, poses before fueling up a vehicle in Guatemala City March 5, 2009. All his life elderly Mexican farmer Gonzalo Cardenas has planted a stalky weed that grows wild in southern Mexico to form a sturdy live fence around his tropical fruit trees. It turns out the weed, jatropha, could be used to fuel jet planes and the Mexican government wants farmers to grow entire fields of it to turn into biodiesel. Picture taken March 5, 2009. To match feature MEXICO-BIOFUEL/ REUTERS/Daniel LeClair (GUATEMALA ENERGY POLITICS ENVIRONMENT SOCIETY)

The Earthrace vessel is seen at Manly Wharf in Sydney January 8, 2009. The vessel, powered with 100% renewable biodiesel fuel, set a world record for a powerboat to circle the globe. Its voyage of over 24,000 nautical miles took 60 days, 23 hours and 49 minutes in June 2008. REUTERS/Daniel Munoz (AUSTRALIA)

US Democratic presidential nominee Senator Barack Obama (D-IL) looks at a sample of bio diesel fuel during a tour of the Pennsylvania Bio Diesel Plant in Monaca, Pennsylvania, August 29, 2008. REUTERS/Jim Young (UNITED STATES) US PRESIDENTIAL ELECTION CAMPAIGN 2008 (USA)

A participant of an eco-friendly team who completed a "Grease to Greece" rally from London to Athens checks his car at an Athens' camping site August 27, 2008. Fuelled only by used cooking fat, eight teams completed the 2,500-mile rally in a bid to promote awareness of alternative bio-fuels. The race, the brainchild of 34-year-old Londoner Andy Pag, took the teams on a 10-day "fat-finding mission" across Europe, begging oil from restaurants, motorway cafes and fast-food joints along the way. REUTERS/Yiorgos Karahalis (GREECE)

A van that took part in a "Grease to Greece" rally from London to Athens makes its way into a camping site in Athens August 27, 2008. Fuelled only by used cooking fat, eight teams completed the 2,500-mile rally in a bid to promote awareness of alternative bio-fuels. The race, the brainchild of 34-year-old Londoner Andy Pag, took the teams on a 10-day "fat-finding mission" across Europe, begging oil from restaurants, motorway cafes and fast-food joints along the way. REUTERS/Yiorgos Karahalis (GREECE)

A woman holds a funnel as she waits to refill the fuel tank of an eco-friendly car that took part in a "Grease to Greece" rally from London to Athens August 27, 2008. Fuelled only by used cooking fat, eight teams completed the 2,500-mile rally in a bid to promote awareness of alternative bio-fuels. The race, the brainchild of 34-year-old Londoner Andy Pag, took the teams on a 10-day "fat-finding mission" across Europe, begging oil from restaurants, motorway cafes and fast-food joints along the way. REUTERS/Yiorgos Karahalis (GREECE)

A sticker is seen on the car of an eco-friendly team that completed a "Grease to Greece" rally from London to Athens August 27, 2008. Fuelled only by used cooking fat, eight teams completed the 2,500-mile rally in a bid to promote awareness of alternative bio-fuels. The race, the brainchild of 34-year-old Londoner Andy Pag, took the teams on a 10-day "fat-finding mission" across Europe, begging oil from restaurants, motorway cafes and fast-food joints along the way. REUTERS/Yiorgos Karahalis (GREECE)

A worker checks rapeseed quality at EcoEnergie's rapeseed biodiesel production plant in Etoy near Geneva, August 13, 2008. EcoEnergie produces 3 million litres of biodiesel per year, equivalent to more than 30 percent of Switzerland's global biodiesel production, while being one of the few companies to operate the full process from seed to oil. REUTERS/Valentin Flauraud (SWITZERLAND)

A worker checks rapeseed quality at EcoEnergie's rapeseed biodiesel production plant in Etoy near Geneva, August 13, 2008. EcoEnergie produces 3 million litres of biodiesel per year, equivalent to more than 30 percent of Switzerland's global biodiesel production, while being one of the few companies to operate the full process from seed to oil. REUTERS/Valentin Flauraud (SWITZERLAND)

Oil and biodiesel containers are pictured at EcoEnergie's rapeseed biodiesel production plant in Etoy, near Geneva, August 13, 2008. EcoEnergie produces 3 million litres of biodiesel per year, equivalent to more than 30 percent of Switzerland's global biodiesel production, while being one of the few companies to operate the full process from seed to oil. REUTERS/Valentin Flauraud (SWITZERLAND)

A vial of cellulosic material sits in a fridge inside a research facility for cellulosic ethanol at the University of Guelph in Guelph, in this May 7, 2008 file photo. In the search for renewable energy, turning low-value materials like switchgrass and corn husks into ethanol to fuel cars is something of a Holy Grail. But scientists on the front lines of this search are finding that making the process commercially and environmentally viable is proving much harder than some of the hype would suggest. To match feature ENERGY-CELLULOSE/ REUTERS/Mark Blinch/Files (CANADA)

A vial of cellulosic material is shown at a research facility for cellulosic ethanol at the University of Guelph in Guelph, in this May 7, 2008 file photo. In the search for renewable energy, turning low-value materials like switchgrass and corn husks into ethanol to fuel cars is something of a Holy Grail. But scientists on the front lines of this search are finding that making the process commercially and environmentally viable is proving much harder than some of the hype would suggest. To match feature ENERGY-CELLULOSE/ REUTERS/Mark Blinch/Files (CANADA)

A process operator shows a handful of corn at the GreenField Ethanol plant in Chatham, Ontario, in this April 10, 2008 file photo. In the search for renewable energy, turning low-value materials like switchgrass and corn husks into ethanol to fuel cars is something of a Holy Grail. But scientists on the front lines of this search are finding that making the process commercially and environmentally viable is proving much harder than some of the hype would suggest. To match feature ENERGY-CELLULOSE/ REUTERS/Mark Blinch/Files (CANADA)

A process operator shows a handful of corn at the GreenField Ethanol plant in Chatham, Ontario, in this April 10, 2008 file photo. In the search for renewable energy, turning low-value materials like switchgrass and corn husks into ethanol to fuel cars is something of a Holy Grail. But scientists on the front lines of this search are finding that making the process commercially and environmentally viable is proving much harder than some of the hype would suggest. To match feature ENERGY-CELLULOSE/ REUTERS/Mark Blinch/Files (CANADA)

A process operator pours ethanol into a bottle at the GreenField Ethanol plant in Chatham, Ontario, in this April 10, 2008 file photo. In the search for renewable energy, turning low-value materials like switchgrass and corn husks into ethanol to fuel cars is something of a Holy Grail. But scientists on the front lines of this search are finding that making the process commercially and environmentally viable is proving much harder than some of the hype would suggest. To match feature ENERGY-CELLULOSE/ REUTERS/Mark Blinch/Files (CANADA)

A process operator is seen on top of fermenters at the GreenField Ethanol plant in Chatham, Ontario, in this April 10, 2008 file photo. In the search for renewable energy, turning low-value materials like switchgrass and corn husks into ethanol to fuel cars is something of a Holy Grail. But scientists on the front lines of this search are finding that making the process commercially and environmentally viable is proving much harder than some of the hype would suggest. To match feature ENERGY-CELLULOSE/ REUTERS/Mark Blinch/Files (CANADA)