Influence of variable feeding on mesophilic and thermophilic co-digestion of Laminaria digitata and cattle manure
Abstract In this study the effect of various feeding ratios on mesophilic (∼35 °C) and thermophilic (∼50 °C) co-digestion of brown algae Laminaria digitata and cattle manure was investigated. Algae input of 15% VS caused no influence on specific methane yield from mesophilic co-digester while deteriorated the process parameters such as the development of propionic acid in total volatile fatty acids (tVFA) pattern of the thermophilic co-digester. The accumulation of tVFA continued for the latter reactor as the feeding ratio of algae enhanced to 24% VS, but the specific methane yield improved dramatically. Same rise in feeding once again showed no improvement in specific methane yield from me…
Semi-continuous feeding and gasification of alfalfa and wheat straw pellets in a lab-scale fluidized bed reactor
Abstract Small scale air-blown fluidized bed gasification of alfalfa and wheat straw pellets were conducted for semi-continuous solid feeding and range of operating conditions varied due to the modifications in equivalence ratio (ER) (0.20–0.35) achieved both by varying solid and air input. Alfalfa pellets displayed an improvement in several gasification variables such as gas lower heating value (∼4.1 MJ/Nm3), specific gas yield (1.66 Nm3/kg), cold gas efficiency (∼42%) and carbon conversion efficiency (∼72%) as ER maximized to 0.35 which was found optimum for this feedstock for the present course of experiments. Gasification parameters of wheat straw pellets on the other hand were characte…
Regulating feeding and increasing methane yield from co-digestion of C5 molasses and cattle manure
Abstract The paper investigated the mesophilic (∼35 °C) and thermophilic (∼50 °C) co-digestion of cattle manure and C5 molasses for a variable organic loading rate (OLR). The small scale continuous reactor experiment revealed that thermophilic treatment yielded a maximum 313 ± 16 L/kg VS methane for the feeding ranged between 50% and 70% C5 (v/v). Mesophilic co-digestion, on the other hand, produced maximum 232 ± 32 L/kg VS methane when feeding was ranged between 31% and 47% C5 (v/v). The feeding strategy of this study was sophistically adjusted owing to the unstable volatile fatty acids (VFA) pattern, developed at different stages of the experiment. Attainable molasses feeding for both the…
Thermochemical gasification of local lignocellulosic biomass via fixed-bed and fluidized-bed reactors
Doktorgradsavhandling The government in Norway aims to double the bioenergy use from 14 TWh to 28 TWh between the year 2008 and 2020. This calls for major changes in the current energy practice and an increase in the biomass based energy applications in the total energy mix. One effort to this end is the replacement of existing space heating oil burners with heat from biomass combustion. However, this strategy alone could not be able to adequately meet the target of further bioenergy expansion. Neither will it help in achieving the Kyoto aim of reducing CO2 emission. So an alternative such as gasification could be a part of the solution. Gasification offers many advantages, but a major conc…
Characterization and pilot scale fluidized bed gasification of herbaceous biomass: A case study on alfalfa pellets
Abstract Pilot-scale bubbling fluidized bed gasification tests of alfalfa pellets were performed at two different operational periods ranged on the basis of the two given equivalence ratio (ER) (the ratio between actual air and the stoichiometric air) namely as 0.25 and 0.30. During the test, the solid feeding rate was kept constant at 4.7 kg/h while the air input was varied and thus the ER. Increasing air from 4.16 to 4.99 N m3/h contributed to the evolution pattern of several parameters such as the rise in gas lower heating value (LHV) and gas yield, the average maximum of which were 4.2 MJ/N m3 and 1.5 N m3/kg respectively. Gas composition was mainly boosted by the concentration of CO, a…
Feasibility analysis of a renewable hybrid energy system with producer gas generator fulfilling remote household electricity demand in Southern Norway
Abstract Hybrid energy system is increasingly emerging as an option to produce energy for the remote areas. This paper presented an economic feasibility analysis of a single standalone house operating with a hybrid power plant consisting of a fixed capacity producer gas generator (2 kWe) and other renewable energy sources (Photovoltaic and wind). The National Renewable Energy Laboratory's Hybrid Optimization Model for Electric Renewable (HOMER) was employed which evaluated techno-economic analysis based on the criteria of net present cost and levelized cost of electricity. Taking the site specific daily average solar radiation, average wind speed and load data into account, renewable hybrid…
Assessing the gasification potential of five woodchips species by employing a lab-scale fixed-bed downdraft reactor
Abstract This paper is aimed to assess the performance of air blown fixed-bed downdraft gasification of local lignocellulosic biomasses which in perspective of Southern Norway are both available and sustainable. Long rotation forest crops birch, oak and spruce, coupled with energy crops poplar and willow were used as feedstocks. The gasification conditions undertaken were widely varied in-terms of air (∼3.20–4.20 N m3/h) and fuel flow (∼1.70–2.10 kg/h) so that the corresponding equivalence ratio (ER) differed (0.19–0.80) and ultimately reflected to other operational parameters such as bed temperature (∼550–760 °C maximum), producer gas yield (∼1.50–2.30 N m3/kg, wet base), cold gas efficien…