January 5, 2010
Every six hours the sun bathes the lands of the earth in as much energy as the world consumes in a year. If we could just find a way to collect and distribute that energy our energy problems would be solved. Unfortunately, most of our energy consumption is in the places with the least sunshine (see insolation map, below.)
Biomass captures and stores the suns energy for later use. In tropical zones biomass grows year round and can be five times more productive than in the temperate zones. Biomass can be converted to denser forms and shipped to where it is needed surprisingly economically. For example, ocean shipping of coal priced at $73/ton from Australia to China only adds about $12/ton to the final cost. Wood chips are bulkier, but they can be made as dense as coal by heating and compressing them into torrefied pellets.
Ocean shipping is amazingly efficient for long distances. Australia has shipped an average of two million tons of coal per month to China so far this year. Ordinary (untorrefied) wood pellets have less than half the energy density of coal, yet Plantation Energy just signed two contracts to ship $130 million worth of pellets to Europe over the next three years. With torrefied pellets shipping costs could be halved so the economics would work out even better. Torrefaction is like coffee roasting. It requires no external energy but uses about 8% of the biomass energy to drive the process. Some of that energy is recovered because pelletizing energy is reduced because the heat-softened lignin in the biomass makes it easier to compress into pellets.
Another big biofuel order recently announced by Valero Energy could be worth up to $3.5 billion dollars. Mission New Energy, an Australian company, will deliver 60 million gallons per year of biodiesel oil from Jatropha crops in Malaysia. Jatropha is a drought-resistant bush with oily seeds that are easily converted to diesel fuel. It is not edible and thrives in tropical climates but requires manual labor for picking the seeds. The all-year growing season, tropical sun and availability of inexpensive labor provides a clean replacement for diesel fuel that can be shipped by the same tankers used for fossil fuel. Valero's annual sales are $120 billion, so this is a serious order.
Mission New Energy works with small farmers to encourage them to plant the bushes on unused and marginal land. They can press their own oil and sell it to the refinery. Larger farmers can refine the oil themselves, as the refining process is very simple compared to petroleum refining.
Jatropha can also be planted on depleted, marginal forestland to restore the land. Mission is careful to maintain a balance between food, fuel and forest so the development is a plus for the community. Unlike factory development, biomass makes it possible for people to remain on their ancestral lands and make money doing clean, outdoor farm work. With industrialization everybody moves to the city to work on dehumanizing production lines. Growing biomass can become a major source of income for the poor and undeveloped tropical countries of the world.
Biomass feedstocks can be grown on soils that have no other uses. For example, Florida has 100,000 acres of phosphate clays that are not stable enough to build on and useless for growing food crops. Leucaena is a bushy legume that grows nicely on these lands. It can be harvested three times per year using standard harvesting machinery to chop it into chips and put it into a truck that follows the harvest machinery. Yields of up to 25 dry tons/acre per year have been obtained but 15 tons is a reasonable average.
Moringa is another legume that has achieved even higher productivity and is tolerant of sulfate acid soils. Legumes need no nitrogen fertilizer because they can fix nitrogen from the air. In semi-desert areas, specially adapted plants like Agave can be grown with no irrigation. Agave stores water in its leaves and heart so that it can continue growing through the long dry seasons that are common in the tropics.
Bamboo has been known to grow as much as 48 inches in a 24-hour period and has been observed growing 39 inches per hour for brief periods. The plants can grow to full height in 3-4 months but die naturally on a six-year cycle.
Clenergen has been growing a variety called Beema Bamboo in India for four years achieving a yield of over 60 tons/acre after four years of cultivation. The company has also been raising a tree called Paulownia for several years with a yield of 40 tons/acre. The company uses a process in which it gasifies the biomass to generate local electrical power but it has announced plans to use gas-to-liquids technology to make liquid fuels out of the syngas. Liquid fuels can be inexpensively shipped around the world by existing tankers.
In fact, biomass can be converted into a wide range of energy carriers for economic shipping. Here are some possibilities and their volume energy density in Watt-hours per liter:
| Crude oil, biodiesel | 8800 watt-hr/liter |
| LNG (Biomethane) | 7216 (must be stored at 268�F) |
| Torrefied Wood Pellets | 6500 |
| Ethanol | 6100 |
| Methanol | 4600 |
| Ammonia | 3100 |
| Wood Pellets | 2777 |
| Liquid Hydrogen | 2600 (must be stored at 423�F) |
| CNG 250 bar biomethane | 2500 |
| Wood chips | 1388 |
| Hydrogen, 150 bar | 405 |
| Lithium Ion Battery | 300 |
The technology for converting biomass to gas and liquid fuels is well known. Methanol, also known as "wood alcohol," is readily produced from biomass through gasification and catalytic synthesis. Methanol fuel cells can convert it to electricity for efficient hybrid electric cars. Methanol has a big advantage because it can be reformed into hydrogen at 200 �C, about half the temperature of other fuels. This makes fast warm up times practical, greatly reducing battery size. During World War II methanol was used extensively in Europe to keep cars running in the face of gasoline shortages.
Methanol and other liquid fuels can be made efficiently on a small scale using microchannel technology, originally developed for the space program. Velosys and Oxford Catalyst have developed a working prototype of a biomass-to-FT-liquids plant that is just being installed in G�ssing, Austria. The 5 ft diameter X 25 ft assembly of 10 microchannel reactors is connected to a biomass gasifier and will output 400 barrels per day of ultraclean synthetic crude oil. This output can be shipped just like crude oil and burned or converted to a full range of clean, carbon-neutral fuels by conventional oil refineries. The microchannel reactor is much more efficient than massive-scale gas-to-liquids plants. The microchannel approach is much like a chemical microprocessor. This kind of small-scale upgrading technology will soon make it possible for tropical areas to convert their plentiful sunshine into easily shipped liquid and solid fuels.
Another approach to exporting solar power involves using electricity as the carrier. The Desertec scheme envisions building HVDC electrical transmission links under the Mediterranean Sea to connect the Sahara desert to the European grid. Massive solar thermal plants in the desert would then supply electricity to all of Europe. Similar concepts for Australia, India, and the USA have been worked out. It still remains to be seen if solar thermal with overnight storage can really be economical. Perhaps someday, but in the meantime, low-tech wood-pellet production is already working at prices almost competitive with coal.
Desertec is like the supercomputer approach while biomass is more like distributed microcomputers. An informal network of low tech, minimal investment biomass operations spread over the world and using existing transportation infrastructure could make a nice living for millions of small low-tech biomass entrepreneurs. Like the Internet, no central control is needed, just a free market that rewards innovation and efficiency. Ocean shipping compares very favorably with HVDC electrical transmission for efficiency. The energy wasted on a long ocean voyage is a tiny percent of the energy being transported.
Already, in 2008 the worldwide pellet market had reached 10 million tons. About 25% of it is already exported to other countries and the market is growing at 25-30% per year. As equipment for upgrading energy density improves, the economics of this market will also improve dramatically. Some power plants in Europe are running entirely on wood pellets but the pellet's lower density means that extensive modification of the power plant are needed. Torrefied pellets can be burned without modifying the power plant. They can be stored, pulverized and burned just like coal. With shipping costs halved, the economics are compelling.
The southern United States has lots of sunshine and rain so it is an excellent biomass growing area. The most efficient model for biomass is to grow it locally in a small radius around a Combined Heat and Power (CHP) plant built where thermal heat is needed. Efficiencies of 90% are often attained because all heat that is normally wasted is used. A recent study showed that the southeastern U.S. could easily be energy self-sufficient. The U.S. government has done some detailed studies showing the dramatic environmental superiority of biomass power over fossil fuel plants. Even conventional farming techniques using fertilizers, insecticides and mechanization turn out to have an excellent energy efficiency factor of 20.5 under a detailed analysis that includes all energy inputs including the energy to make the farm machinery. With all of the energy inputs subtracted, the plantation analyzed yielded a net energy production of 125 MWh per acre per year.
You may have heard that biomass is much less efficient than photovoltaic cells. Solar cells are typically rated around 10% efficiency but this rating ignores the fact that the average energy from the sun is only about 20% of peak. The real average efficiency then is .1 X .2 = 2%. If we look at land use of some real projects now on the drawing boards we find that the latest photovoltaic, parabolic and tower projects all use about 5-6 acres per peak MW.
The Saguaro 1-MW parabolic trough plant near Phoenix for example, generates 2000 MWh of electricity annually, using 15.8 acres. That's 130 MWh per acre per year. The 125 MWh figure for the biomass plantation that I mentioned above is for heating value. Electricity generation can be 80% efficient if it is done where wasted thermal energy can be used as in CHP plants. So biomass is at least in the same ballpark as other solar technologies for land use but much cheaper to implement, store and transport than direct electrical generation.
Some terrible mistakes have been made in recent years when tropical rain forests and peat bogs were burned for agricultural development. Big trees should not be replaced by a succession of little trees. We must structure carbon trading so that such acts are taxed and only sound actions are rewarded. Clearing land by open-air burning is common today. If simple, inexpensive equipment was available for upgrading biomass to shippable products, logging waste could be put to good use replacing coal power.
Biomass can help keep the lights on while we build more renewable capacity. If we don't use it, coal will certainly fill the gap. Sweden, Norway and Finland have been making heavy use of biomass for power for decades. They have structured their laws to encourage good stewardship of the land. We can do the same thing internationally by defining good rules for carbon trading.
Download my free renewable energy book, Fuel Free: Living Well Without Fossil Fuels here.
Photo by: TheMarker 
23/01/2010
