Green energy from different feedstock processed under anaerobic conditions

V. Skorupskaitė¹, V. Makarevičienė¹,*, G. Šiaudinis² and V. Zajančauskaitė³

¹Aleksandras Stulginskis University, Faculty of Forest Sciences and Ecology, Institute of Environment and Ecology, Studentų Str. 11, LT53361 Akademija, Kauno district, Lithuania; *Correspondence: virginija.skorupskaite@asu.lt
²Vėžaičiai Branch of Lithuanian Research Centre for Agriculture and Forestry, Gargždų str. 29, LT96216 Vezaiciai, Klaipėda district, Lithuania
³Klaipėda University, Faculty of Marine Technology, Department of technological process. Herkaus Manto Str. 84, LT92294 Klaipėda, Lithuania

Abstract:

The possible use of energy crops and aquaculture for bioenergy production has only recently become a research target, so there is little information on their properties and advantages. The aim of this study was to investigate the possible use of cup plant, as well as marine and freshwater algae (Scenedesmus sp. and Chlorella sp.) for biogas production. Research of a batch anaerobic digestion process at a mesophilic temperature were performed using wet wastewater sludge, cattle manure, fresh microalgae biomass and dry marine algae, cup plant biomass and mixtures of these materials. The highest biogas yield (541.28 ml g-1 VS) was obtained by using a new feedstock from the microalgae Scenedesmus sp. biomass. That yield was 1.4 times higher than the biogas yield from cattle manure and 15% lower than the biogas yield from wastewater sludge. It was found that adding microalgae biomass to a cattle manure substrate increases biogas production approx. 1.5 times. The highest methane concentration in biogas produced from microalgae ranges from 64.87% to 66.66% and exceeds the methane amount (64.26%) in biogas produced from wastewater sludge. The methane amount in biogas produced from cattle manure, cup plant and marine algae biomass is lower than 60%. In addition, it was found that it is possible to produce 5,092.3 m3 of biogas or 113 GJ of energy from 1 ha of harvested cup plant biomass.

Key words:

biogas production, cattle manure, cup plant, marine algae, microalgae, wastewater sludge.

Wood ash and wastewater sludge recycling success in fast- growing deciduous tree – birch and alder plantations

D. Lazdiņa*, K. Liepiņš, A. Bārdule, J. Liepiņš and A. Bārdulis

¹Latvia State Forest Research Institute Silava, Riga Street 111 2169, Salaspils,Latvia; *Correspondence: dagnija.lazdina@silava.lv

Abstract:

Due to the increasing of wood as energy renewable resource in power and heat plantsthe amount of wood ash as waste will increase. Wood ash contains plant macronutrientelements P, K and different elements as micronutrients, only organic and nitrogen are missing.Wastewater sludge from small municipalities is usually clean, first-class material and contains alot of nitrogen and phosphorus. Wood ash can be a good fertiliser and a liming material not onlyfor acid organic soils, but also for mineral soils, but with a less significant effect on the treegrowth in first seasons than a nitrogen rich fertiliser wastewater sludge.The effects that wood ash and wastewater sludge have on the increment and survival of treeswere tested during the years 2011 and 2012 on loam and loamy soils at plantations of blackalder, birch and grey alder, and they were compared with the results collected in the previousresearch started in 2005. It was observed that wood ash in the first two seasons did notsignificantly increase the growth of silver birch, as wastewater sludge did, but it had a positiveeffect on the annual increment of grey alder. Fertilisation of the whole field decreased thesurvival of trees because of weed competition and different injuries.The aim of the study was to evaluate the growth of fast-growing deciduous trees seedlings asshort rotation crop under fertilisation of wood ash, and wastewater sludge on former agriculturalland.

Key words: