Suitability of semi-natural grassland biomass for combustion and the effect of quality optimization strategies Bettina Tonn1, Ulrich Thumm2, Wilhelm Claupein2 1 University of Göttingen, 2 University of Hohenheim 24th General Meeting of the EGF 3-7 June 2012 Lublin

Benefits of bioenergy generation from grassland biomass Introduction Benefits of bioenergy generation from grassland biomass Production function renewable energy Non-production functions biodiversity landscape … Semi-natural grassland Fibre concentrations high Combustion small-scale   technological development 

Biomass quality challenges for combustion Environmentally harmful emissions high biomass ash concentrations  dust emissions high biomass N concentrations  NOx emissions  environmental issues / legal restrictions Ash high-temperature behaviour high biomass K and Cl concentrations  corrosion, fouling high proportion of K / low proportion of Ca and Mg in biomass ash  slagging  risk of damages / decreased lifespan of combustor

Questions 1) High variability of biomass quality of semi-natural grasslands  relative importance of: botanical composition cutting date site effects 2) Quality optimization strategies from other herbaceous biofuels  effect on semi-natural grassland biomass of: a) Delayed harvest in winter / early spring b) Leaching of unwanted substances through rain after cutting ? ?

Materials and methods Natural variability 6 sites 5 harvest dates June July August September October 2 biomass fractions Grasses Forbs Winter harvest 2 additional harvests December February Leaching Control 10 min leaching ≈ 30-40 mm rain 120 min leaching ≈ > 70 mm rain 3 treatmens

Materials and methods Sample analysis ash, N, Cl, K, Ca, Mg concentrations ash high-temperature behaviour: visual examination after 2 h at 1000 °C Statistical analysis linear contrasts of log-transformed chemical composition parameters for: June harvest – October harvest forbs – grasses site maximum – site minimum October harvest – winter harvest dates unleached control – leaching treatments (expressed as proportion of first contrast variable)

Influence of natural variability K Cl Ca Mg N ash Harvest date June – Oct June K Cl Ca Mg N ash Biomass fraction forbs – grasses forbs K Cl Ca Mg N ash Site max – min max -0.4 -0.2 0.2 0.4 0.6 0.8 1.0 linear contrast (fraction of first contrast variable) error bars: 95 % confidence interval -0.4 -0.2 0.2 0.4 0.6 0.8 1

Influence of winter harvest K Cl Ca Mg N ash December harvest Dec – Oct Dec K Cl Ca Mg N ash February harvest Feb – Oct Feb -0.4 -0.2 0.2 0.4 0.6 0.8 1.0 linear contrast (fraction of first contrast variable) error bars: 95 % confidence interval -0.4 -0.2 0.2 0.4 0.6 0.8 1

Influence of leaching 10 min leaching control – leaching control K Cl Ca Mg N ash 10 min leaching control – leaching control K Cl Ca Mg N ash 120 min leaching control – leaching control -0.4 -0.2 0.2 0.4 0.6 0.8 1.0 linear contrast (fraction of first contrast variable) error bars: 95 % confidence interval

Ash melting behaviour (1000 °C) Wet hay meadow Intermediate hay meadow June September September July loose slightly sintered strongly sintered molten K/(Ca+Mg): 0.3 K/(Ca+Mg): 1.1 K/(Ca+Mg): 1.9 K/(Ca+Mg): 2.6

Conclusions Ash, N ( emissions) relatively low natural variability little influence of winter harvest / leaching  technical solutions necessary K, Cl, K/(Ca+Mg) ratio ( ash high-temperature behaviour) strong effects of site and botanical composition  opportunity for selection of high-quality low-quality biomass strong positive effect of winter harvest / leaching  further quality improvement possible

Thank you! Bettina Tonn btonn@gwdg.de

Ash melting behaviour (1000 °C) Winter harvest Leaching (Ca+Mg)n (%) 80 60 40 20 Kn (%) Sin (%) 100 (Ca+Mg)n (%) 80 60 40 20 Kn (%) Sin (%) 100 grasses June-Oct forbs June-Oct whole plot Dec, Feb control 10 min leaching 120 min leaching Ash melting classes: loose slightly sintered strongly sintered molten

Natural variability of Ash and N concentrations Teil 1 Grasses Forbs Sites 120 dry calcerous grassland I Ash 120 90 90 dry calcerous grassland II Aschegehalt (mg g-1) 60 Aschegehalt (mg g-1) 60 dry hay meadow 30 30 Iintermediate hay meadow wet hay meadow June July Aug Sep Oct June July Aug Sep Oct N 30 30 tall sedge swamp 20 20 N-Gehalt (mg g-1) N-Gehalt (mg g-1) 10 10 June July Aug Sep Oct June July Aug Sep Oct

Natural variability of K and Cl concentrations Grasses Forbs Sites K 30 30 dry calcerous grassland I dry calcerous grassland II 20 20 K conc. (mg g-1) K conc.(mg g-1) dry hay meadow 10 10 Iintermediate hay meadow wet hay meadow June July Aug Sep Oct June July Aug Sep Oct 16 Cl 16 tall sedge swamp 12 12 Cl conc. (mg g-1) 8 Cl conc. (mg g-1) 8 4 4 June July Aug Sep Oct June July Aug Sep Oct

Leaching efficiency (July harvest) Ash Nitrogen Sites 100 16 dry calcerous grassland I 80 12 60 dry calcerous grassland II ash conc. (mg g-1) N conc. (mg g-1) 8 40 *** all *** 4 20 * dry hay meadow 10 120 10 120 Iintermediate hay meadow leaching (min) wet hay meadow Potassium Chlorine 24 all *** alle *** 6 all *** all *** 18 4 *** / : * K conc. (mg g-1) 12 Cl conc. (mg g-1) significantly different from control (0 min). 2 6 10 120 10 120 leaching (min)

Winter harvest Ash Nitrogen ** ** Potassium Chlorine *** *** *** *** Sites 120 20 dry calcerous grassland I 90 15 dry calcerous grassland II Aschegehalt (mg g-1) 60 N-Gehalt (mg g-1) 10 ** ** 30 5 dry hay meadow Iintermediate hay meadow Oct Dec Feb Oct Dec Feb wet hay meadow Potassium Chlorine 15 all *** all *** 12 all *** all *** tall sedge swamp 10 8 K-Gehalt (mg g-1) Cl-Gehalt (mg g-1) *** / : ** 5 4 significantly different from October values Oct Dec Feb Oct Dec Feb

Leaching methods simulated rain Standardized laboratory method 30-40 mm irrigation 10 min leaching > 70 mm irrigation 120 min leaching

Leaching method comparison Tonn et al. (2011) Grass Forage Sci 66:464-473

Effect of leaching on ash melting behaviour (1000 °C) Control 10 min leachiching 120 min leaching 1 mm