Miscanthus among perennial bioenergy crops in northern EU, has been promoted during last decade for heat and power production. After cultivating more than 12,000 hectares in UK, too low average yields (10-12 odt/ha per year) and high costs of delivered biomass (60-140 €/odt) are becoming major constraints suggesting that other options could be better suited in higher latitudes. We analyze main barriers for Miscanthus expansion and suggest alternative cheaper feedstock and approach.

Miscanthus, also known as elephant grass some times, is another specialized energy crop being grown in the UK.  It grows to about 3 metres in height per annum and can produce very high yields with little by way of secondary inputs like pesticides or fertilizer. As a perennial it also sequesters more carbon to the soil than most annual crops. The UK government believes there is significant scope to expand the UK supply of biomass, without any detrimental effect on food supplies and in a sustainable manner, by sourcing an additional one million dry tonnes of wood per annum from currently unmanaged woodland in England alone, and from increasing the recovery of wood for energy from managed woodland and other sources of wood waste products across the UK. In addition, perennial energy crops produced in the UK have the potential to use up to a further 350,000 hectares across the country by 2020, bringing the total land availability for biofuel and energy crops to around a million hectares, equivalent to 17% of total UK arable land. Additionally, Miscanthus is one energy grass with really low ashes and chloride in the biomass and could be really well suited for power stations that admit many sources of biomass.

However, many governmental officers and researchers’ are realizing that UK national average yields for this C4 “warm” perennial grass is lower than 12 odt/ha (oven dried tons per ha) each year. They are giving average yields and performance in thousands of hectares accounting many years. It is clear that the potential yield of the species is high. It has been reported in several areas of the world to be more than 35 odt/ha.yr. Our internal reports have information from locations like Ohio, Arkansas, Illinois, Pisa (Italy), several tropical and subotropical countries (including Central America, Asian countries and Africa) and Australia and New Zealand too). The fact is that now many stakeholders and governmental agencies in UK are starting to admit that this warm grass requires warm climate, water availability and soil fertility. And this is a serious concern for some people in UK.

Our reports from several locations in European countries mention that the costs required for planting operations (rhizomes) range from  2000 up to 5000 € per one hecatre (operations included). We know about several cases in large scale projects with better results in North America, South America and Asia. A high yield is required to breakeven point if costs are high as in Europe, and this is particularly crucial if  the plantation lifetime is lower than 10 years.

A recent (2013) study from Alexander and Moran (Scottish Agricultural College) showed that a broader mix of crops would be more suitable for UK conditions to reduce risks and increase acceptance by farmers.

Considering a high establishment cost with rhizomes and personnel planting propagation materials, most  cost estimations  rank 80-140 € per dried ton (on the truck, with equivalent to zero % moisture). That includes of course land leased, fertilizers, land preparation first year and successive operations as well as  yearly harvesting costs. All those items divided an average yield of 12 odt/ha will result in too high cost for the industry. If confirmed, other “cheaper” (lower inputs and yields but lower production costs per ton) might be a more reliable alternative in large scale agriculture under the conditions in UK. In the news from FCC 300 tons are expected from 30 ha. That’s only 10 tons/ha, same amount several perennial grasses established from seeds produce with half of the cost (in €/t). Even other crops like Virginia fanpetals could offer lower delivered biomass costs.

Once we read news like the FCC harvest averages yields,we wonder if farmers and companies know about realistic yield expectations and lifespan of Miscanthus plantations  considering UK experiences and current knowledge and research. We also wonder if the industry is aware about what they have to expect from this crop in Northern Europe or Northern US.

Plantation lifetime and realistic yields

The faact is that in cold environments a tropical grass (warm C4 photosynthetic methabolism pathway converting CO2 in glucose) will be not as efficient as in New Zealand, Argentina, Brazil or many other areas in Southern Europe. Most research plots in Italy (Pisa) or in irrigated conditions of the Mediterranean, have showed higher yields compared to those in UK and Poland. Even in Germany some plots give higher yields. Daylight period, radiation interception, leaf area index and biomass produced are all affected as we move to higher latitudes.

Several studies show that a plantation’s lifespan of 20 years with stable  productivity is  realistic but it is true that most experiences take information from experimental small plots at university sites and not in large scale projects on demonstrative programs or in large parcels.  There is a curve and long term progress with decreasing yields from the 8 -10th year. But that performance will mostly depend on productivity and management as well as soil fertility. As farmers cut every year, yields may decrease from a certain point and rhizome reserves can be depleted determining different performance and yield. A more realistic perspective tohave is a productivity curve of about 10 years or even less in some regions  considering long term experiences.

That facts are difficult to prove in commercial plots, since most long run data come from small plots with border effects and several environment/genotype interactions that condition results and reliable conclusions when expecting productivity in large scale investments. Moreover, some researchers also argue on the fact warm grasses in temperate climates like UK are not always the best alternative to produce stable low cost biomass at the farm. Is this fact conditioning farmers to establish new plantations in UK? Should we have much more than about 10,000 hectares in England? Should national average yields be much higher than 12 odt/ha per year during the lifespan in a crop that requires thousands of pounds to establish just one hectare?

Results confirm earlier research findings that converting from annual to perennial crops and from traditional crops or production systems to new ones are important barriers.

Some possible alternatives to consider

Temparate areas seem best suited for tall high yielding C3 species (in particular “cool grasses”). They have lower requirements and can reach similar yields compared to Miscanthus and Switchgrass (another C4 crop best suited in lower latitudes). Analyzing productivity of most bioenergy crops, most research studies show that willows, poplars, eucalyptus and many C3 grasses have yields ranging from 6 to 12 odt/ha per year. Why not planting the chepeast option?

Many perennials can be establish with very low cost from seeds and produce similar yields (10 tons or more per ha per year with typical costs from 35 to 60 €/odt are very feasible in UK).  C3 grasses and hardy grasses like tall wheatgrass but even  several reeds and phalaris arundinacea may produce good results some times. In particular Virginia fanpetals have been tried inPoland, Latvia and UK with better results compared to Miscanthus.

Virginia fanpetals. This unique species, when harvested in the dry stage, has applications in the bioenergy, insulation and cellulose-paper industries.

Sencescence and natural drying is a key issue to obtain cheaper crops producing 10-14 odt/ha-yr with lower establishment costs and easy renovation every 15 years even in marginal areas. No rhizomes, no expensive planting material or even plough requirements may limit the expansion of those species. Some good publications about grasslands can be read in our previous post here.

Traditional forage techniques with adaptation for biomas production systems are  feasible. Our experience with perennial energy grasses that can have  pasture renovation, non tillage establishment and re-sowing after 10 years using some herbicides show us much lower costs and feasibility application with no rhizome planting or high inputs. Additionally, most machinery equipment is already there and available for most farmers at the time Policy reforms in Europe are making less profitable grassland management for grazing and livestock. There is enough evidence that many species could provide cheaper biomass under similar conditions.

In higher latitudes, Tall wheatgrass plantations are taking place and our group is leading several experiments including cooperation with groups in Argentina, United States, Hungary, Poland and highlands of Spain.  Despite of the ability of this species to tolerate drought and be a hardy winter perennial grass adapted to saline and alcaline soils, when it is cultivated in wetter areas, its performance is much better. Tall wheatgrass may yield as much as 16 dried tons per hectare each year with two cuttings.