Waste to energy technologies for solid waste management a case study of Uganda

Municipal solid waste management is one of the major environmental problems of developing countries. Investments in solid waste management would not only translate into jobs and income but also a cleaner environment. Over years a number of solid waste management technologies have been carried out in many developing parts of the world. Some were successful in generating lasting impacts on the improvement of solid waste management, however, many technologies failed due to unsustainability. This is partly attributed to differences in waste characteristics between developed countries and the less developed countries and the resource constraints in less developed countries. On the other hand, less developed countries are also known for being energy deprived and thus energy recovery as sustainable waste management technology is advocated for in these countries. This paper seeks to review and assess the energy recovery potential from the various sustainable waste technologies in Uganda. The advantages attached to such technologies will be assessed and evaluated. In a further step, a comparative analysis with traditional energy sources like hydro-electricity power and petroleum products powered generators is also presented and discussed. This study concludes that renewable energy sources present Uganda with a rare opportunity to elevate millions out of energy poverty

Assessment of the suitability of pineapple waste as feedstock for vermicomposting

Declining soil fertility is a challenge to sustainable agricultural production in sub-Saharan Africa with a case of Uganda. However, the large volumes of agricultural waste generated from pineapples can be converted into soil conditioners through vermicomposting. by the use of earthworms. Several types of agricultural waste have been studied extensively as vermicompost feedstock, but little work exists on pineapple waste. The objective of this study was to investigate the suitability of pineapple waste for vermicomposting. To achieve this, an assessment of the physicochemical properties of fresh, pre-composted pineapple waste, and the resultant vermicompost, and determination of the optimal feeding rate and stocking density were performed.  The study revealed that pre-composting reduced the moisture content (28.8%), VOC (10.3%), and increased the pH (56.8%) which was helpful in waste stabilization as well as in the mass reduction of the waste. Vermicomposting after pre- composting increased the bulk density (92.3%), ash content (25.4%), pH (10%), EC (14.3%), total phosphorus (20.9%) and total potassium (28.4%) but decreased the moisture content (29.1%), VOC (11.8%), organic carbon (81.4%), total nitrogen (21.3%) and the C:N ratio (76.4%) of the pineapple waste hence giving a more stabilized and mineralized vermicompost. The study further revealed an optimal feeding rate of 2 kg feeds/kg worms and a stocking density of 1 kg worms/m2 for complete nitrogen mineralization of the pineapple waste and 1 kg feeds/kg worms and 0.5 kg worms/m2 for higher phosphorus concentrations. The degradation of the pineapple waste by earthworms demonstrated the practicability of vermicomposting as a simple and low-cost technology of converting pineapple waste into an effective nutrient rich soil amendment.

VERMIFILTRATION AS A LOW-COST TECHNOLOGY FOR MANAGING DAIRY WASTEWATER

Dairy manure needs to be treated to mitigate its adverse impacts on the environment. Vermifiltration, an emerging low-cost and environmentally friendly wastewater treatment, is one such potential treatment. For this study, we evaluated the efficacy of a vermifilter for treating dairy wastewater with respect to effluent quality and potential mitigations of air emissions. A pilot-scale unit was installed on a commercial dairy for these evaluations. Additional studies, at a lab-scale, investigated the effects of earthworm density, organic loading rate, and hydraulic loading rate on the performance of the vermifilter. Wastewater parameters of interest included: total solids, total suspended solids, chemical oxygen demand, total nitrogen, total ammonia-nitrogen, nitrate-nitrogen, total phosphorus, and orthophosphate. The vermifilter achieved organic, nutrients, and solids reduction efficiencies of up to 90%. Results indicated that vermifiltration has a high potential to reduce organics, nutrients, and solids concentration in dairy wastewater. Results also indicated potential reductions of up to 100% of ammonia, methane, and nitrous oxide emissions, implying that vermifilters have the potential for mitigating gaseous emissions from dairy wastewater. With respect to earthworm density, organics, nutrients, and solids; reductions of up to 95% were observed, with higher reductions occurring at higher earthworm densities (>10,000 worms m-3). Eisenia fetida densities beyond 10,000 worm m-3 did not improve the performance of the vermifilter unit towards reducing either organics, nutrients, or solids in dairy wastewater. Higher reductions of organics, solids, and nutrient occurred at lower HLR (< 1 m3 m-2 d-1) and OLR (< 2.5 kg [COD] m-2 d-1). These findings suggested that HLR <1 m3 m-2 d-1 and OLR < 2.5 kg [COD] m-2 d-1 are desirable in vermifilters when the goal is to achieve higher organics, solids, and nutrients reductions during treatment of dairy wastewater. Overall, this research shows that vermifilters can effectively be used to treat dairy wastewater

A short review on the potential of coffee husk gasification for sustainable energy in Uganda [version 1; referees: 2 approved]

Agricultural biomass is widely recognized as a clean and renewable energy source, with increasing potential to replace conventional fossil fuels in the energy market. Uganda, like other developing countries, has a high dependency (91%) on wood fuel, leading to environmental degradation. With a coffee production of 233 Metric Tonnes per annum, relating to 46.6 Mega Tonnes of coffee husks from processing, transforming these husks into syngas through gasification can contribute to resolving the existing energy challenges. The objective of this article is to briefly review the energy potential of coffee husks through gasification, and how the gasification process could increase energy recoveries for coffee farmers. Previous  findings indicate that the 46.6 Mega Tonnes per year of coffee husks generated in Uganda, with a heating value of 18.34 MJ/kg, is capable of generating 24 GWh of energy. This will address a 0.7% portion of the energy situation in Uganda, while protecting the environment

Potential for Use of Pineapple Waste to Enhance Soil Fertility on Smallholder Organic Farming in Kayunga District, Uganda

Soil exhaustion and nutrient depletion are major constraints to pineapple farming in Uganda. This study explored potential for using on-farm waste from pineapple farming to conserve soil fertility and enhance agricultural productivity. Data collection was done using key informant interviews, focus group discussions, and a semi structured survey questionnaire administered to 109 randomly selected pineapple farmers and processors. The data was analysed in SPSS to generate descriptive statistics for selected variables followed by cross tabulation to explore linkages between the variables. Results indicate that farmers engaged in pineapple farming, have diverse socioeconomic backgrounds but activities engaged in are not significantly associated with socioeconomic variables examined except farming experience and gender. The major challenges faced by the farmers included soil exhaustion, lack of appropriate technologies, inappropriate pineapple waste management and decline in yield. It was noted that strategies used by farmers employing use of on-farm waste have not yielded significant contribution and as such farmers resort to use of off-farm manure which is expensive and increasingly hard to secure. It was recommended that a sustainable technology harnessing the abundant but underutilised on-farm biomass waste be developed to produce a highly nutrient-rich soil conditioner to enhance pineapple yield and as such empower the farmers