Multiple-criteria decision analysis techniques for anaerobic digester technology assessment.

Effective decision-making requires the evaluation of several criteria rather than a single, preferred criterion. The best decision options (alternatives) are recommended to decision-makers when a multi-criteria decision problem is addressed. This study develops a multi-criteria selection method for the assessment of small-scale anaerobic digester technology by combining two existing methods. The Simple Multi-Attribute Rating Technique (SMART) and the Analytical Hierarchy Process (AHP) approaches of multiple-criteria decision analysis were used as a decision support tool, and the preferred anaerobic digester technology was selected from a list of eleven potential small-scale digester technologies used in low to middle-income countries. These techniques were applied under two scenarios for a case study in the South African smallholder farmers. Scenario 1 involves a subsistence smallholder farming context, while scenario 2 involves a commercially oriented smallholder farming context. The overall results revealed that the DIY Biobag and Puxin digester design models achieved 82.1 and 73.7 % preference in comparison to other digester technologies for scenarios 1 and 2, respectively. The Biobag digester technology achieved the highest ranking, which is consistent with the significant cost advantage and technical characteristics of the technology. However, for those households with sufficient access to funds for the initial expenditure, the method identifies the Puxin digester as the most appropriate alternative, excluding cases where underground construction is not possible. The AGAMA BiogasPro digester was ranked in the second position in both scenarios. A sensitivity analysis was conducted to determine the effect of changes in the assessment criteria weights and found the selected alternatives stable and robust. Finally, it can be concluded that the developed technology selection model contributed a knowledge-based framework to be used in various situations by different decision-makers, thereby providing a method applicable to particular local conditions to identify the most suitable technology choices.

Effect of storage condition on the nutritional and anti-nutritional composition of kurkura (Ziziphus mauritiana Lam.) fruit from North-Eastern Ethiopia.

Ziziphus mauritiana is used as food and medicine. It is very nutritive and contains high amounts of calcium, phosphorus, iron, vitamin C, and beta-carotene. To choose an appropriate technique for fruit preservation, this study evaluated the effect of temperature and time on the nutritional and anti-nutritional qualities of Ziziphus mauritiana fruit harvested from Kobo Woreda in North-Eastern Ethiopia. This study assessed the impact of preservation parameters on the nutritional and anti-nutritional properties of Ziziphus mauritiana fruit, such as storage temperature and preservation day (time). Ziziphus mauritiana fruit was also analyzed to evaluate storage temperature and preservation day on its nutritional and antinutritional composition and found moisture content (5.25-10.99%), ash content (4.74-10.70%), crude fiber (3.81-17.88), fat (0.49-2.16), nitrogen content (1.01-1.8%), protein content (6.33-11.27), phytate content (67.27-659.33 mg/100 g m), and tannin content (3842.46-16577.80 mg/100 g m). The findings revealed that both individual and interaction effects were highly significant differences (p-value, 0.0001) in each nutritional and antinutritional content of the fruit. The results of this study showed that it was possible to store Ziziphus mauritiana fruit using plastic bags (High-Density Polyethylene Bags), and further deep-freezing the fruit had the best effect on preserving it in its fresh state (without damage) for up to 45 days.

Bioenergy potential from crop residue biomass resources in Ethiopia.

Using crop statistics (2020-21), publicly accessible data, standard procedures and literature, this study estimates the bioenergy potential of crop biomass residues in all regions of Ethiopia. The assessment considered 44 different types of residues from 30 different crops grown in Ethiopia. The country generates 69 569-105 522 kt y-1 gross crop residue biomass, of which 42 621-72 194 kt y-1 (or 61-68% of gross) are estimated as recoverable for bioenergy production. Amongst all the eleven regions, Oromia produces the highest amount of recoverable crop residue (45%) at region level. Cereals produce the highest recoverable crop residue (80%), followed by fruit crops (8%). Maize (36%) and sorghum (29%) are the two crops that produce the highest recoverable residue amongst all the crops. The estimated 559-1144 PJ y-1 bioenergy potential for Ethiopia from recoverable crop residue varies by region and ranges from 0,15 to 0,37 PJ y-1 (Afar) to 254-521 PJ y-1 (Oromia). Decentralized energy planning using crop residues in Ethiopian regions is expected to benefit from the produced data, which will help the country's overall growth in renewable energy. Biological and thermo-chemical conversion systems that are now in various stages of demonstration, commercialization, development, and research can convert biomass into energy. Performing research and development, establishing a database for local biomass resources, and developing a unified bioenergy unit and policy with all stakeholder's participation and engagement are all critical aspects of Ethiopia's sustainable bioenergy sector. Furthermore, value chain analysis of biomass feedstock, capacity building and awareness creation, and decentralized models development are all important for the country's bioenergy development.

Probabilistic techno-economic assessment of anaerobic digestion predicts economic benefits to smallholder farmers with quantifiable certainty.

Anaerobic digestion (AD) technology holds numerous potential benefits for farmers, however, challenges persist in terms of implementation costs and sustainability in developing countries. This paper presents a probabilistic techno-economic assessment tool for AD. A clear distinction is made between direct financial feasibility and wider (socio) economic feasibility. The tool identifies the technical- and economic factors influencing the returns of a particular AD process as well as the sensitivity of model predictions to variations in the value of the identified factors using a Monte Carlo approach. The tool is applied to assess the feasibility of a smallholder farm-based AD installation under a variety of substrates and operating conditions as an illustrative case study, where on-going flows of costs and benefits were considered over a 15-year period and discounted at a rate of 8%. The results of the case study revealed that the installation of a 10 m3 smallholder farm-based anaerobic digester are likely to be financially and economically viable with a financial benefit-cost ratio of 1.30-1.38 and an economic benefit-cost ratio ranged from 5.49 to 6.01. Risk assessment results confirmed the strong economic feasibility of a smallholder farm-based AD implementation: under the most conservative cost estimates, there is a 73% probability of achieving a financial benefit-cost ratio > 1, while there is a 96.6% probability of achieving an economic benefit-cost ratio > 1. The case study demonstrated the utility of probabilistic techno-economic assessments for informed decision making, a tool which can be readily generalized to other settings.

Prioritization and selection of high fuelwood producing plant species at Boset District, Central Ethiopia: an ethnobotanical approach.

BACKGROUND: In Ethiopia, about 92.3% of all the fuelwood (firewood and/or charcoal) is consumed for cooking, heating and lighting purposes by domestic households and the demand is growing from 10 to 14%. However, there are little/no practical experiences or documented indigenous knowledge on how traditional people identify and select high fuelwood producing plant species with short rotation periods at Boset District. Therefore, the present study was aimed at: (1) selecting and documenting high fuelwood producing plant species at Boset District; (2) identifying major predictor variables that influence the prioritization and selection of species; and (3) develop a Generalized Linear Model (GLM) to predict the selection of species. METHODS: A total of 96 informants comprising 59 men and 37 women between the ages of 18 and 81 were sampled. Data were collected using structured interviews, guided field walk, discussions and field observations. RESULTS: Collected data indicated that 88.5% of the informants involved in firewood collection, while 90% practiced charcoal making. A total of 1533.60 Birr per household on average was earned annually from this activity. A total of 25 fuelwood producing plant species were identified and documented at Boset District. Of these, Acacia senegal, Acacia tortilis and Acacia robusta were the three best prioritized and selected indigenous high fuelwood producing species. Prosopis juliflora, Parthenium hysterophorus, Azadirachta indica, Calotropis procera, Cryptostegia grandiflora, Lantana camara and Senna occidentalis further grouped under introduced fuelwood species. Prediction of GLM assured sampled Kebeles and source of income generated from fuelwood species positively and significantly (p < 0.001) related to selection of species. Higher efficiency to provide energy and heat; little or no smoke or soot; easier to cut and split the wood and easier availability were some of the main selection criteria. CONCLUSIONS: This study provides valuable information in selecting and documenting of high fuelwood producing plant species for proper management and sustainable use at Boset District. The three most selected species (A. senegal, A. tortilis and A. robusta) should be further evaluated at laboratory to determine their calorific value and combustion characteristics.