“Silvergrass, silvergrass grows on the hills / Blossoms in the valleys / With leaves but no branches / Standing alone / Bows down its head when the wind blows....” A Taiwanese folk song portrays silvergrass flowing over mountain ridges and running alongside riverbanks. As the birds build their nests and search for food among the silvergrass, an earlier generation of Taiwanese also enjoyed a close relationship with the plant. Farmers used the stalks to make brooms, thatch for roofs, windbreak fences, and toys for the children. The grasses were also a good source of forage, and were used as religious symbols by indigenous people to ward off evil.

Sadly, when Taiwan was industrialized, silvergrass lost its value and became simply a weed. But every dog has his day. In recent years, Western science has rediscovered the plant, which is now regarded as one of the new stars of biomass fuel. Because of its unique geography, Taiwan possesses a great variety of silvergrass species, and is playing an important role in international research.

When most people in Taiwan talk about silvergrass, they mean Mis­can­thus flor­id­ulus, which blossoms around Dragon Boat Festival, but it’s in fact only one of a range of species. There are in fact eight species and varieties in Taiwan, including M. sin­en­sis var. gla­ber, M. sin­en­sis var. for­mo­sa­nus, and M. trans­mor­ri­son­en­sis, growing in low, medium and high altitude areas respectively, and M. con­den­sa­tus, growing on Lanyu and Green Island. Another three species have been discovered but not yet confirmed.

“Silvergrass can be seen almost everywhere in Taiwan, aside from the Jia­nan Plain because of its long dry season,” says Chiang Tzen-Yuh, professor in the Department of Life Sciences, National Cheng Kung University (NCKU). Silvergrass is found mainly in East and Southeast Asia, and Taiwan and Japan have the greatest variety. Even in China’s vast lands, only a few species can be found.

Xu Zai­wen, director of He­huan­shan Experimental Station of the Council of Agriculture’s Endemic Species Research Institute, says that silvergrass is a very vigorous plant, and compared with reeds, which need a marshy environment, it will survive in almost any conditions: on river­banks, in the mountains, in arid or salty regions near the sea, in the snow or in areas ravaged by fire, and even in places polluted by heavy metals.

Wu Wen-teng (left), director of the Research Center for Energy Technology and Strategy, NCKU, and Chiang Tzen-Yuh (right), professor in the Department of Life Sciences, NCKU, are pushing research into silvergrass biomass energy. Through a charring process, silvergrass becomes charcoal and can be burned with coal to generate power, reducing fossil carbon emissions. It’s an area well worth the investment.

Because of its robustness and vigor, silvergrass has been chosen as the object of research into second-generation biofuels.

The first generation of biofuels created a number of issues. Growing huge amounts of sugarcane, corn, soybeans and palm oil to produce bio-ethanol and bio-diesel actually inevitably takes land away from human food production and exacerbates food shortages. Some nations in Central and South America and Southeast Asia log trees in rainforests in order to plant biofuel crops, creating environmental havoc and reducing the forest’s ability to absorb carbon. So scientists have been looking for ways to develop second-generation biomass energy, using agricultural waste such as rice straw and sugarcane fiber (“bagasse”), which can be processed for use as fuel or to extract ethanol. They’re also on the lookout for new plant species that won’t harm the environment.

UK and European Union studies have looked at over 100 plants, and found that Mis­can­thus with its great vitality, highly efficient photosynthesis (silvergrass grows larger and faster than many other plants for the same amount of absorbed sunlight) and large biomass, is ideal for biofuel production.

Taiwan has actively invested in Mis­can­thus research as a result of these findings. Research scientists in the UK identified two major groups of silvergrass: M. floridulus, and M. sinensis (M. sinensis var. glaber, M. sinensis var. formosanus, M. transmorrisonensis, and M. condensatus). The latter group has the greatest range of variations. But after samples were collected from various Asian regions, the conclusion was reached that China’s silvergrass is relatively small in size and in the number of varieties available. Taiwan, on the other hand, has better quality and greater diversity of silvergrass; as a result, the UK actively sought cooperation with Taiwan to import silvergrass into Britain.

In recent years, Chiayi Agricultural Experimental Station has invested a great deal in silvergrass research, experimenting with different varieties, planting methods and harvest times to create the best economic outcomes.

While Taiwan has been exporting Mis­can­thus genetic material, it has also begun research into biomass energy. These studies include possibilities such as processing silvergrass into a solid fuel as a partial substitute for coal in power generation; or transforming silvergrass into ethanol or oil and mixing these with petrol or diesel as fuel for vehicles. However, these proposals all have different technological and cost issues that need to be resolved.

To create a solid fuel from silvergrass, the Research Center for Energy Technology and Strategy, NCKU, has used pyrolysis (the thermochemical decomposition of organic material at high temperatures with limited oxygen or without oxygen) to produce charcoal. Dr. Chen Guanbang from the research center notes that while sun-drying and compression may be the cheapest method, the resultant fuel lacks burning efficiency because of retained moisture. And since the pieces are quite large, it’s not easy to store (it can tend to rot) or transport. While heating silvergrass to create charcoal can solve these problems, it’s not very cost-efficient when electricity is used. Thus, the research center is experimenting with recycled pyrolysis gas to char silvergrass, saving energy. They have also developed a mobile pyrolysis furnace to process the material onsite to save freight costs.

Wu Wen-teng, director of the research center, says that one hectare of land can produce 38 metric tons of silvergrass annually, and then through the charring process, can convert 40% into charcoal. Burning this amount of silvergrass charcoal with coal in a power plant will reduce fossil carbon emissions by the equivalent of burning 15 t of coal.

But what about the economics? Assuming that a metric ton of coal costs US$80, if a farmer plants silvergrass on one hectare of land which can produce 15 t of charcoal, they could gain an annual revenue of US$1200. With an average monthly yield of US$100 per hectare, there seems to be no incentive for farmers. “The key issue is going to be the carbon tax,” says Wu. Assuming a carbon tax that levies NT$800–1000 per metric ton of carbon, if 1 t of coal emits 2.6 t of carbon dioxide, then 15 t of silvergrass charcoal can save NT$40,000 in carbon tax, effectively reducing costs for the power plant, and may in turn increase the economic return to growers.

Production levels are closely associated with careful selection of species, and planting and harvesting techniques. Huang Zhe­lun, a research fellow at the Council of Agriculture’s Chiayi Agricultural Experimental Station, says that Taiwan’s climate is perfect for growing M. floridulus. After two years of experimentation, they have found that harvesting twice a year delivers no more product than harvesting just once, the best distance between plants is one meter, and one hectare of land can yield 50 metric tons.

Silvergrass is an extremely robust plant, and can survive almost anywhere: on riverbanks, in the mountains, in arid or salty regions, in areas ravaged by fire, and even in places polluted by heavy metals. The photo shows silvergrass growing in Jinguashi mining area.

Apart from its suitability as raw material for solid fuel, making ethanol from silvergrass is another area for research, but one that requires sophisticated techniques. The US, world leader in fermentation technology, sought an opportunity to cooperate with Taiwan in this area three years ago.

Chiang Tzen-Yuh notes that the cooperation agreement was signed by the US Department of Agriculture and Taiwan’s Council of Agriculture: in the US, a team from the University of Illinois is responsible for research and development of fermentation technology, including the selection of suitable cultures to improve fermentation efficiency; in Taiwan, the NCKU is responsible for finding suitable strains and for genetic enhancement. Maurice Ku, vice-president of National Chiayi University, is in charge of research into photosynthesis efficiency.

Species which are strongly disease-resistant and contain less lignin are preferred. This latter quality means they decompose more readily. And through traditional breeding or genetic modification, it is hoped to generate cultivars with three to five times the biomass in order to reduce production costs.

Second-generation biomass energy is based on the concept of using microorganisms and enzymes to decompose agricultural waste or weed cellulose. Since the first generation needed greater fossil-fuel energy to cultivate and harvest crops, the energy input tended to negate any benefits gained from lower CO2 emissions. Hence its viability was thrown into question. The key to successful second-generation biomass energy, on the other hand, lies largely in breakthroughs in the area of cellulose decomposition. Because of the self-defensive nature of plant biology, the structure of cell walls is very complex, which means that they are very difficult to ferment and decompose. Many countries have invested in research in this area, and there are currently a number of cultures available that are able to digest cellulose. As a result, costs are expected to fall gradually.

NCKU’s Research Center for Energy Technology and Strategy, National Yunlin University of Science and Technology, and Kao Yuan University have all invested in research into making pyrolysis oil from silvergrass, producing fuel by mixing pyrolysis oil with diesel. Wu notes that pyrolysis oil contains water, unlike other bio-diesel substances that are able to mix easily with diesel. To use pyrolysis oil with diesel, however, vehicles need to be modified. Research is ongoing in this area.

Should silvergrass be made into solid fuel, ethanol or pyrolysis oil? Which has the greatest potential? Solid fuel technology is well developed, Chiang says, so in the short term silvergrass and silvergrass charcoal will be the main focus for development. The US and Europe have begun the commercial generation of power using solid biofuel. Transforming silvergrass into ethanol will become the focus in the medium and long terms.

According to an Irish study, if 10% of Europe’s arable lands were used to grow silvergrass, it could generate up to 9–10% of the EU’s electricity. Planting silvergrass on hillsides and roadsides is currently being trialed in the EU.

The Council of Agriculture notes that silvergrass has long roots, so if large quantities were planted on Taiwan’s fallow lands, the areas would be difficult to rehabilitate for normal farming. Thus, the council has a more conservative view. Alternative energy policies of the Bureau of Energy currently focus on solar and wind power, and biomass energy remains a minor option. Chiang believes that if the government supported the planting of silvergrass, while fallow lands may be unsuitable, there are other suitable areas such as often-flooded or salty areas on Taiwan’s west coast.

The EU has imported a large amount of foreign silvergrass for trial plantings. Although tight controls have been applied, there is always some potential risk of disturbing the ecological balance. However, in order to develop alternative energies, they need to choose the least disadvantageous option. Taiwan, on the other hand, has abundant quantities of silvergrass growing naturally. The government should implement its new-generation biomass energy policy as early as possible, otherwise the advanced technologies being developed by Taiwan’s research groups may be lost abroad. In that case, Taiwan would miss a golden opportunity to become more energy self-sufficient.