Comparative testing of energy yields from micro-algal biomass cultures processed via anaerobic digestion

Abstract

. Comparative testing of energy yields from microalgal biomass cultures processed via anaerobic digestion. Renewable Energy, 87,[744][745][746][747][748][749][750][751][752][753] http://www.sciencedirect.com/science/article/pii/S0960148115304286 doi:10.1016/j.renene.2015.11.009 __________________________________________________________________________________ Comparative testing of energy yields from micro-algal biomass cultures processed via anaerobic digestion Keiron P. Roberts, Sonia Heaven, Charles J. Banks Faculty of Engineering and the Environment, University of Southampton, Southampton, SO17 1BJ, UK (Email K.P. Roberts@soton.ac.uk, S.Heaven@soton.ac.uk, C.J.Banks@soton.ac.uk) Abstract Although digestion of micro-algal biomass was first suggested in the 1950s, there is still only limited information available for assessment of its potential. The research examined six laboratory-grown marine and freshwater micro-algae and two samples from large-scale cultivation systems. Biomass composition was characterised to allow prediction of potentially available energy using the Buswell equation, with calorific values as a benchmark for energy recovery. Biochemical methane potential tests were analysed using a pseudo-parallel first order model to estimate kinetic coefficients and proportions of readily-biodegradable carbon. Chemical composition was used to assess potential interferences from nitrogen and sulphur components. Volatile solids (VS) conversion to methane showed a broad range, from 0.161-0.435 L CH 4 g -1 VS; while conversion of calorific value ranged from 26.4-79.2%. Methane productivity of laboratory-grown species was estimated from growth rate, measured by changes in optical density in batch culture, and biomass yield based on an assumed harvested solids content. Volumetric productivity was 0.04-0.08 L CH 4 L -1 culture day -1 , the highest from the marine species Thalassiosira pseudonana. Estimated methane productivity of the large-scale raceway was lower at 0.01 L CH 4 L -1 day -1 . The approach used offers a means of screening for methane productivity per unit of cultivation under standard conditions.

Anaerobic Co-digestion of the Energy Crop Sida hermaphrodita and Microalgae Biomass for Enhanced Biogas Production

“…In turn, the yield of methane production from the microalgae biomass may reach 240-307 mL/g VS for Chlorella vulgaris and 210-261 mL/g VS for Scenedesmus sp. (Ras et al 2011;Zamalloa et al 2012;Roberts et al 2016), which was similar to our findings of 315.71 mL/g VS for the substrate consisting of Chlorella sp. and Scenedesmus sp.…”

Biogas production from undiluted chicken manure and maize silage: A study of ammonia inhibition in high solids anaerobic digestion

“…TAN, FAN total VFA and pH in R1-R4 during the experimental period are shown in Fig This long-term TAN accumulation in the digesters is attributable to the high-nitrogen feedstock combined with low rates of conversion of nitrogen into biomass and limited losses into the gas phase as NH 3 . It is recognised, however, that multiple factors affect the final TAN concentration in a digester (Lindorfer et al, 2012, Roberts et al, 2016 as well as its partitioning into the free and ionic forms. It is also likely that methanogens and other members of the anaerobic consortium can acclimate to ammonia, and it is therefore not surprising that inhibition of the digestion process has been reported over a wide range of TAN concentrations (Chen et al, 2008).…”

Energy Balance of Biogas Production from Microalgae: Effect of Harvesting Method, Multiple Raceways, Scale of Plant and Combined Heat and Power Generation

“…This was equivalent to an estimated specific methane yield of 0.33 g·CH 4 ·g −1 of Volatile solids (VS) for algae with a 20% lipid content, corresponding to the higher end of the range for quoted methane yields [15,20,38]. Recent studies have found a 60% yield for Dunaliella salina [39] and 59%-79% yield for five commercially exploited microalgal species [40].…”