A Model for Testing Compressive and Flexural Strength of Sisal Fibre Reinforced Compressed Earth Blocks in the Absence of Laboratory Facilities

This study proposes a method of indirectly evaluating strength and therefore durability characteristics of compressed earth blocks in the absence of the normally expensive laboratory facilities. The method, with respect to compressed earth blocks reinforced with sisal fibres, is recommended for application particularly in rural areas of Africa. The developed method entails loading a compressed earth block sample with increasing amounts of weight till the sample raptures (total dead weight) under the load. The weight is then taken and a comparison is made with the standard value of compressive and flexural strength of the said sample. A conversion factor between this developed method and the conventional way of determining compressive and flexural strength has been computed. It has been established that the total dead weight is 47.25 times the flexural strength while the same is 66.4 times the compressive strength. The primary advantage of the proposed method is that it can easily be adapted at village level by people who have little scientific knowledge

Acceptance, Operational Challenges and Conceptual Optimization of Biodigester System in Embu Prison

This research was conducted within the Kenyan context in Embu prison on a pioneering and fully operational, since 2011, biodigester system. After three years of operation it was imperative to assess the functionality of the system and also the acceptance level by the users and beneficiaries. This research was significant as it synthesizes the true-life experiences from Biodigester utilizing rare input-human excreta. The study was a cross-sectional descriptive research which sought to examine the operational practices and challenges of the biodigester, alongside with factors influencing the adoption of biogas technology. To achieve this, the study conducted regular field visits to Embu prison, administered interviews and distributed questionnaires (designed in English and in Kiswahili language). The data was organized, edited, coded and analyzed using the Microsoft Excel and Statistical Package for Social Sciences (SPSS). Response rate of detainees was 76%, while for staff it was 43%. To address the issue of gas accumulation at night hours and fully utilize the potentials of human excreta, the study proposed to incorporate microbial fuel cells (for electricity production). Conceptualization and preliminary design of optimized system was conducted according to fundamental engineering design principles. To select the best alternative design a pair-wise comparison known as the drop and re-vote (D&R) method was used in this study. The study confirmed that biodigester in Embu prison is an appropriate solution to produce clean renewable energy. Therefore it is recommended to pursue and replicate this approach in prisons in other areas and in different public institutions of Kenya. The study also identified several directions for further research; the most important one is to conduct detailed structural design of the proposed configuration including economical evaluation of the system. The results and discussions may be also applicable to other countries or regions with similar conditions. Keywords: biogas, biodigester, human excreta, Kenya

Impacts of detritivore diversity loss on instream decomposition are greatest in the tropics

It is unclear whether stream detritivore diversity enhances decomposition across climates. Here the authors manipulate litter diversity and examine detritivore assemblages in a globally distributed stream litterbag experiment, finding a positive diversity-decomposition relationship stronger in tropical streams, where detritivore diversity is lower

Impacts of detritivore diversity loss on instream decomposition are greatest in the tropics

The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, strongest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, particularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent