Comparative Study on Biogas Yields of Plug Flow and Batch Reactors fed with Rice Straw at Mesophilic Temperature

The present energy crisis has stimulated various research activities to evaluate energy potentials of renewable energy sources. Improper disposal of rice straw constitutes nuisance to our environment especially in most rice producing states of Nigeria. To this end, the biogas potential of rice straw was evaluated in Plug Flow Reactor (PFR) and Batch Reactor (BR) operated at mesophilic temperature (37oC). A 140-litre capacity PFR was filled with 105 litres previously digested sludge as inoculum. The loading of the rice straw into the reactor was commenced at a low LR of 0.5 goTS/l.d and was increased weekly by 0.5 goTS/l.d until a LR of 4.5 goTS/l.d was attained. For the batch reactor, 10.15 g of rice straw was loaded into each of the two digestion vessels. Two additional vessels were filled with inoculum as control. For the PFR, the biogas produced was collected using gas bags and then measured with a multi-chamber rotor gas meter. The gas analyzes was done with an Infrared Gas Detector. The scale wet gas collectors were used for the batch reactor and the gas measurement done with the gas analyzer (Model GA 2000). It was established that the biogas yields increased with increase in LR (PFR).  The highest biogas yields of 0.20 l/goS and 0.167 l/goS were recorded in PFR and BR, respectively. In all, continuous feeding using PFR (at optimum LR) has been established to be better than batch feeding using BR at mesophilic temperature. Keywords: Renewable energy; rice straw; Biogas; Loading rate; Plug flow reacto

Effect of Co-Digestion on Anaerobic Digestion of Cattle Slurry with Maize Cob at Mesophilic Temperature

Attempt was made to determine the effect of co-digestion on anaerobic digestion of cattle slurry (CS) with maize cob (MC). The experiment was carried out in a laboratory scale batch experiment. Cow Slurry and Maize Cobs were co-digested at ratios 3:1, 1:1 and 1:3 using the percentage volatile solid of each substrate. Co-digestion of CS with MC at 3:1, 1:1 and 3:1 under mesophilic temperature (37oC) gave biogas yields of 453.38, 417.30 and 428.92 lN/kgoDM respectively while the methane yields were 334.18, 323.63 and 323.27 lNCH4/kgoDM respectively. Methane concentrations of 73.71, 77.55 and 75.37% were obtained at CS: MC combinations of 3:1, 1:1 and 1:3 respectively. The study revealed that co-digesting CS with MC at ratio 3:1 is optimum for biogas production. Keywords: co-digestion, cattle slurry, maize cob, batch experiment, mesophilic temperatur

An Assessment of Potential Resources for Biomass Energy in Nigeria

Nigeria is a developing country with an insufficient supply of energy to meet the continuously growing demand. However, there are several biomass resources available within the country. This paper presents a desk review, which investigates the potential resources for biomass energy generation within the country. Energy policies to aid biomass use as an energy source within the country were also reviewed. Biomass resources identified within Nigeria include forest residues, agricultural residues, human and animal wastes, aquatic biomass, and energy crops. However, several of the resources, particularly agricultural residues, have competing uses, such as livestock feed and soil rejuvenation. An estimation of the technical energy potential of the biomass resources revealed that about 2.33 EJ could be generated from the available resources in Nigeria. Agricultural residues have an energy potential of about 1.09 EJ, with cassava, maize, oil palm, plantain, rice, and sorghum being the major contributors. Animal wastes, municipal solid waste, and forest residues have energy potentials of 0.65, 0.11, and 0.05 EJ, respectively. The potentials of wood fuel and charcoal are 0.38 and 0.05 EJ, respectively. The study found that despite the available potential and existing policies, not much has been done in the implementation of large-scale bioenergy within the country. However, there has been laboratory and research-scale investigations. The review suggests that more policies and stronger enforcement will aid bioenergy development within the country. From the review, it has been suggested that the agricultural sector needs to be developed to generate more biomass resources. More research, development, and implementation have to be carried out on biomass resources and bioenergy generation processes. The production of non-edible energy crops in marginal lands should also be considered prime to the development of bioenergy within the country

Effect of Co-Digestion on Anaerobic Digestion of Pig Slurry with Maize Cob at Mesophilic Temperature

The 21st century faces the problem of growing energy consumption and diminishing supplies of fossil fuels, which has led to researches on the use of renewable energy sources and, consequently, the development of new technological processes of energy production. Pig slurry and maize stalk constitute nuisance to our environment and should be got rid of. Co-digestion has been found by researchers to improve the product of anaerobic digestion.  This work determined the effect of co-digestion on anaerobic digestion of pig slurry with maize cob. Pig slurry and maize cobs were co-digested at ratios 3:1, 1:1 and 1:3 using the percentage volatile solid of each substrate. The experiment was carried out in a laboratory scale batch experiment. The digester was fed with pig slurry-maize cob mixtures calculated for the selected ratios based on the volatile solid (VS) concentration of the selected substrates. Co-digestion of pig slurry with maize cobs at ratios 3:1, 1:1 and 3:1 at mesophilic temperature (37oC) gave biogas yields of 0.323, 0.392 and 0.486m3/kgoDM respectively while the methane yields were 0.240, 0.305 and 0.358 m3CH4/kgoDM respectively. From the fresh mass of the substrate, biogas yields of 0.035, 0.057 and 0.109 m3/kgFM were obtained for pig slurry-maize cob ratios of 3:1, 1:1 and 1:3 respectively while the methane yields from the fresh mass for the same ratios were 0.026, 0.044 and 0.080 CH4/kgFM respectively. Co-digestion of pig slurry with maize cob was found to have methane concentrations of 74.30, 77.90 and 73.68% at pig slurry/maize cob combinations of 3:1, 1:1 and 1:3 respectively. The study revealed that co-digesting pig slurry with maize cob at ratio 1:3 is optimum for biogas production (yields). Keywords: Co-digestion, pig slurry, maize cob, batch experiment, mesophilic temperature

Energy Use Efficiency of Melon (Colocynthis Citrullus) Production under Different Tillage Methods

Since mechanization is inevitable and is associated with increase in productivity, there is need to find the most appropriate tillage method in crop production that minimizes energy consumption, enhance profitability and reduce environmental damage from fossil fuel related emission. This research investigates the energy use efficiency in melon production in three tillage methods (reduced, minimum and maximum). Human power, machinery, diesel fuel, fertilizers, seed and pesticides energy inputs were used during the cultivation of melon. Input and output energy analysis method was used to quantify the input and output energy in each of the tillage methods during the production of melon. The energy indices of melon production determined are; energy efficiency, energy productivity, specific energy, net energy and energy efficiency index. The total energy required per hectare in reduced, minimum and maximum tillage were 4528.29, 7191.07 and 8325.64 MJ/ha while the output energy were found to be 8112, 10404 and 10752 MJ/ha, respectively. The energy efficiency were estimated to be 1.79, 1.45 and 1.29 while net energy were found to be 3583.71, 3212.93 and 2426.36 MJ/ha for reduced, minimum and maximum tillage methods, respectively. The result revealed that maximum tillage is better than both reduced and minimum tillage in terms of energy efficiency and net energy gain. Keywords: energy, melon, tillage, energy efficiency, net energy DOI: 10.7176/JETP/9-9-05 Publication date: December 31st 201

Determination of Energy Balance and Economic Analysis of Cucumber (Cucumis Sativus) Production in Tillage Methods

Energy whatever might be its source viz. human, animal, machine, electricity, solar, seed, chemical, fertilizer, gasoline or diesel has become a crucial input of agriculture right from preparatory tillage to the disposal of farm produce, energy input is necessary. This study investigates the energy balance and economic analysis of cucumber production in tillage methods. A tin of 50 g of treated cucumber seeds was planted in three different tillage systems namely; reduced, minimum and maximum tillage using foot dibbling method. Human power, machinery, diesel fuel, fertilizer, seed and pesticides were various forms of energy inputs used during the field cultivation of cucumber in the selected tillage methods. Input and output method of energy analysis was used to analyze the amount of input and output energies in each of the three tillage systems used in the production of cucumber. The calculated energy indices determined are energy ratio, energy productivity, specific energy, net energy and energy efficiency index. The result revealed that the highest total energy input and output values of 8694.09 and 8359.33 MJha-1 were estimated in maximum tillage, minimum tillage has an average values of 7774.42 and 12015 MJha-1, while the least average values of 5688.26 and 12736.67 MJha-1 were estimated in reduced tillage, respectively. The highest benefit–cost ratio of 2.94 was found in minimum tillage, followed by maximum tillage with a value of 2.35, while least value of 2.08 was estimated in reduced tillage. Keywords: Cucumber, tillage, energy, energy indices and net profit DOI: 10.7176/JETP/10-1-08 Publication date: February 28th 202

Drying parameters of wild lettuce (Lactuca taraxaxifolia L) affected by different drying methods

This study focused on the effect of drying method on drying properties of wild lettuce leaves. The fresh wild lettuce was washed thoroughly to remove extraneous parts and subjected to pretreatments by dipping 200 g of vegetable samples into the water (1.5w/v) solution with 0.3% sodium metabisulphite held at room temperature. The pre-treated and untreated leaves were weighed and loaded in stainless steel tray and subjected to drying under cabinet dryer, open-sun drying and solar dryer. The wild lettuce drying curve exhibits a gentle downward curve, i.e. a high moisture loss at the early period of drying for all the drying methods used. The effective moisture diffusivity and activation energy were determined. The effective moisture diffusivity increased with the increase in temperature of drying. This study showed that post harvest losses of wild letuce can be minimized through drying, using mechnical devices or open sun drying, which is one of the oldest preservation processes available to the mankind

Influence of Tree Species, Harvesting Method and Storage on Energy Demand and Wood Chip Quality When Chipping Poplar, Willow and Black Locust

The cultivation of fast-growing wood (e.g., poplar, willow or black locust) in short rotation coppices and agroforestry systems presents an opportunity for producing biomass sustainably in the agricultural sector. Cost-efficient agricultural wood production requires the availability of high-performance machinery and methods with which high-quality wood chips can be produced at low cost. It is known from harvesting short rotation coppices in practice that both the wood chip quality and the performance of the harvesting machinery depend on a variety of factors (e.g., harvesting method, weather conditions, tree species). That is why this study examines in detail the influence of the tree species (different varieties of poplar, willow, black locust) and the wood condition (fresh, stored or dried, frozen) on the specific energy demand for comminution in a stationary drum chipper and on the particle size distribution of the wood chips produced. For all the tree species examined, the chipping of dried as well as frozen stems was connected with a significant increase in the specific energy demand for comminution. An increase of 31% has been measured if poplar stems are chipped in frozen conditions (max. 6.31 kWh t−1). Drying led to an increase of 59% for dried willow stems (max. 6.67 kWh t−1). Drying and frost had also an influence on the size and quality of the wood chips, but no globally significant connection could be established for the examined tree varieties

Influence of Tree Species, Harvesting Method and Storage on Energy Demand and Wood Chip Quality When Chipping Poplar, Willow and Black Locust

The cultivation of fast-growing wood (e.g., poplar, willow or black locust) in short rotation coppices and agroforestry systems presents an opportunity for producing biomass sustainably in the agricultural sector. Cost-efficient agricultural wood production requires the availability of high-performance machinery and methods with which high-quality wood chips can be produced at low cost. It is known from harvesting short rotation coppices in practice that both the wood chip quality and the performance of the harvesting machinery depend on a variety of factors (e.g., harvesting method, weather conditions, tree species). That is why this study examines in detail the influence of the tree species (different varieties of poplar, willow, black locust) and the wood condition (fresh, stored or dried, frozen) on the specific energy demand for comminution in a stationary drum chipper and on the particle size distribution of the wood chips produced. For all the tree species examined, the chipping of dried as well as frozen stems was connected with a significant increase in the specific energy demand for comminution. An increase of 31% has been measured if poplar stems are chipped in frozen conditions (max. 6.31 kWh t−1). Drying led to an increase of 59% for dried willow stems (max. 6.67 kWh t−1). Drying and frost had also an influence on the size and quality of the wood chips, but no globally significant connection could be established for the examined tree varieties