The potential of Estonian semi-natural grasslands for bioenergy production

High biodiversity of Estonian semi-natural grasslands can only be maintained through continuous management. One option for the usage of biomass from these areas is bioenergy production, if both the herbaceous biomass yield and the chemical characteristics of the cut meet the needs. In 2007 the largest average annual biomass yield per area was achieved in floodplain meadows (5.7 t dry mass/ha), which also have the highest potential for biomass production among Estonian semi-natural grasslands (more than 113,000 t dry mass). The area of mesic meadows is larger, but due to lower average yield per area (2.5 t dry mass/ha), the potential of this meadow type was less than half of that of floodplain meadows (53,000 t dry mass). The corresponding numbers for wooded meadows were 1.6 t dry mass/ha and 12,000 t dry mass, respectively. Chemical characteristics of herbaceous biomass from wooded meadows significantly differed from mesic and floodplain meadows, giving the highest values of Ca, K, Mg, crude protein and ash (1.3%, 2.4%, 0.3%, 10.9% and 9.5% of the dry biomass, respectively). The energetic value of the biomass from different meadow types varied between 18.1 kJ/g and 18.6 kJ/g. Therefore, various options for bioenergy conversion should be considered depending on the local plant community and restrictions to the harvest time.