Sustainable cropping of reed canary grass for energy use

The increasing use of fossil fuel is plagued with problems leading to interest in alternative sources of energies. Bioenergy or biomass energy remains today s important renewable energy source that can contribute to reducing the overall consumption of fossil fuel and can move energy systems towards sustainability and supply security. However, doubts on sustainability impede the acceptance of bioenergy. Hence, the sustainable cropping of reed canary grass (Phalaris arundinacea L., RCG), an established perennial energy grass, was studied. Important sustainability criteria were considered, namely; land use, biomass productivity, emission of greenhouse gas nitrous oxide (N2O) and biodiversity. The general aim of the study was to develop farming methods that would provide biomass feedstock of RCG in a sustainable manner. Field and glasshouse experiments were carried out at the University of Helsinki, Finland, during 2008 to 2013. The suitability of problematic acid sulphate soils managed with raised water tables for cropping RCG was investigated in lysimeter experiments. Growth parameters were measured and biomass yield and energy qualities were determined. In field conditions with soils classified as Gleyic Stagnosol, RCG was supplied with N from inorganic fertilizer and N fixed into soil by intercropped legume galega (Galega orientalis Lam.) and its biomass yields and mineral element composition and other energy qualities were determined. Gases were collected from these fields using closed chambers and greenhouse gas N2O emissions were analysed by gas chromatography. The crop and crop mixture effects on earthworm communities were determined by the extraction of earthworms using mustard oil and manual separation from soil. Reed canary grass grew well in acid sulphate soils and even performed better by producing more biomass with better quality when the water table was raised to reduce acidity and to avoid environmental hazards. Carbon was also sequestered into the soil by RCG root biomass. In the field experiment, RCG galega mixtures produced equally good biomass yields and of better energy quality than the fertilized RCG counterpart. The annual cumulative emissions of N2O from mixtures were marginally lower than those from fertilized RCG soils. Although fertilized RCG produced twice as much biomass and correspondingly higher nitrogen and energy yields, its low emission of N2O per ton of dry matter or per unit of harvestable bioenergy was not significantly different from that of the mixtures. Mixtures also enhanced earthworm abundance and species numbers compared to pure RCG stands. Therefore cropping an RCG galega mixture for biofuel may supply a good quantity of biomass feedstock, result in lower N2O gas fluxes, and sustain earthworm biodiversity but requires management to maintain grass as the major component. Using managed acid sulphate soils for perennial energy cropping will help to reduce the tension between food and energy crop production over arable land and may improve the negative perception of bioenergy as a whole. A 25% Galega- 75% RCG mix has the potential to replace N fertilizer input during energy crop cultivation, meaning reduced cost of production and more income for energy crop farmers. Moreover soil macrofauna diversity will be conserved. With reduced N2O gas emission, this grass-legume mixture could make a significant contribution in mitigating climate change and its effects. All these will come a long way to help in making bioenergy more sustainable.Ruokohelpin viljely bioenergian lähteeksi ekologisesti kestävällä tavalla Bioenergia on tärkeä uusiutuva energialähde, joka voi johtaa uusiutumattoman (fossiilisen) energian kokonaiskäytön vähenemiseen. Bioenergian käytön yleistymistä haittaavat kuitenkin epäilyt tämän energiamuodon ekologisesta kestävyydestä. Ruokohelpi on asemansa vakiinnuttanut monivuotinen energiakasvi, jonka tuotannon kestävyyttä tässä työssä tutkittiin. Pyrkimyksenä oli kehittää kestäviä viljelymenetelmiä ruokohelpibiomassan tuottamiseksi energiantuotantoa varten. Helsingin yliopistossa vuosina 2008-2013 järjestetyissä kenttä- ja kasvihuonekokeissa tutkittiin ruokohelven viljelyä happamilla sulfaattimailla. Kasvihuonekokeissa tutkittiin happamien sulfaattimaiden soveltuvuutta ruokohelven viljelyyn, kun pohjaveden pintaa pidettiin lähellä maan pintaa säätösalaojituksen ja kastelun avulla. Kenttäkokeissa ruokohelpeä lannoitettiin väkilannoitetypellä, tai ruokohelpeä ja typpeä sitovaa vuohenhernettä kasvatettiin seosviljelmänä. Kokeissa seurattiin kasvihuoneilmiötä aiheuttavan dityppioksidin (N2O) päästöjä sekä tutkittiin puhdaskasvustojen ja seosviljelmien vaikutuksia lierojen esiintymiseen. Ruokohelpi kasvoi hyvin happamalla sulfaattimaalla, ja lähellä maan pintaa pidetty pohjavesi jopa lisäsi sadon määrää ja laatua. Ruokohelven suuri juurimassa johti myös hiilen sitoutumiseen maahan. Kenttäkokeessa ruokohelven ja vuohenherneen seoskasvusto tuotti yhtä suuren määrän ja bioenergiantuotannon kannalta laadultaan parempaa biomassaa kuin väkilannoitettu puhdasviljelmä. Vuotuiset N2O-päästöt olivat sekakasvustossa hieman pienemmät kuin lannoitetun puhdaskasvuston päästöt. Sekakasvuston maaperässä oli myös enemmän lieroyksilöitä ja erilaisia lierolajeja

Sustainable bioenergy cropping: growing reed canarygrass in acid suphate soils

The response of reed canary grass to water logging, acidity and dissolved metals will be studied in the field as well as in a controlled environment using large monoliths of undisturbed acid suphate soil taken into PVC tubes

High moisture acid sulphate soil effects on reed canary grass

To examine the suitability of acid sulphate soils for perennial energy cropping and specifically to provide information on the responses of reed canary grass (Phalaris arundinacea L.) to raised water levels, a management option for these problematic soils, large core lysimeters of undisturbed field acid sulphate soil were taken into PVC tubes equipped with ground water level control and measurement instruments, planted with reed canary grass, and studied during the period 2008 - 2011. Two treatments; high water content (HWC, 20 cm below soil surface) and low water content (LWC, 70 cm below soil surface, considered normal for acid sulphate soils) were considered and there were 4 replicates. Tiller height, net photosynthesis, and above ground biomass at harvest were measured and Al, Fe, K, Si and S were analysed using ICP-OES. Tillers in HWC lysimeters were 30 and 23% taller than those in LWC lysimeters (P = 0.003, P = 0.002) in September 2009 and 2010 respectively. Net photosynthesis was higher in LWC grasses, although the margin was significant only in year 2009 (P = 0.04). Spring 2009, dry matter yields were almost the same in both treatments, but in 2010 and 2011, HWC grasses yielded 43% and 37 % more than LWC (P = 0.001 in both years), respectively. Dry matter harvested in spring of both 2010 and 2011 contained more Al, K, S and Si in the LWC treatment than in HWC treatment, whereas the concentration of Fe was higher in HWC treatment in 2009 and 2010. It was concluded that reed canary grass, an established bioenergy crop, grows well in acid sulphate soils and can perform better when the water table is raised to reduce acidity and prevent environmental hazards. This could serve as management option and a solution to the problems cause by acid sulphate soils and same time reduce the controversy about the use of bioenergy crops on arable land