Browsing by Author "Simbaya, J."

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Heavy metal distribution in soils of some urban and peri-urban horticultural farms in Botswana
(RUFORUM, 2014-07) Obuseng, L.C.; Meulenberg, F. Pule; Mubyana, T. John; Mpuisang, T.; Agbenin, J.; Oluko, Patrick Samba; Norton, J.; Okalebo, J.R.; Omondi, E.; N’getich, W.; Shikuku, D.S.; Okeyo, J.M.; Odhiambo, J.A.; Norton, U.; Ashilenje, D.; Wangoli, J.W.; Otiende, Verrah Akinyi; Mwanga, E.F.; Gitau, A.N.; Christiane, T.; Ernest, M.; Manuel, Joana; Matusse, Joaquim; Pimentel, Andréa Eloisa Bueno; Hess, S.; Hatab, A.A.; Da Silva, L.M.; Boly, H.; Glym, C.; Chibinga, O.C.; Musimba, N.M.; Nyangito, M.; Simbaya, J.; Elhag, M. Muna; Sulieman, M. Hussein
Despite the fact that there is high usage of agrochemicals and use of urban waste water for irrigation, the concentration of potentially toxic metals in urban and peri-urban agriculture (UPA) farms has not been widely investigated in Botswana. The study focused on quantitative assessment of potentially toxic metals in horticultural production under UPA. Crops which are cultivated at the selected study sites include spinach (Spinacia oleracea L.), rape (Brassica rapa var. rapa.), cabbage (Brassica oleracea var. capitata), green pepper (Capsicum annum) and tomato (Solanum lycopersicum). Two farms from areas surrounding Gaborone namely Glenn Valley and Mmankgodi, were sampled for the determination of total heavy metals concentration in soils. In Glenn Valley secondary treated waste water is used for irrigation while in Mmankgodi underground water is used. Four soil profile pits were dug at each farm and soil samples of 20 cm increment were collected from the surface to a depth of 100 cm. Results showed concentration ranges of 0.12 - 1.22 mg/ L for Cr, 0.09 - 0.47 mg/L for Cu and from 0.01 - 0.24 mg/L for Pb. Copper and Chromium were above threshold levels for crop production (Cu 0.2 mg/L, Cr 0.1 mg/L) as per Food and Agriculture (FAO) standards and Botswana Bureau of Standards (BOBs), while Pb concentration was significantly higher at Glenn Valley than Mmankgodi, but below recommended threshold levels of 2.0 mg/L. These results are a wake-up call that policies on the use of sewage effluent and agrochemicals should be enforced.
The potential of beetle and termite fibre hydrolytic crude extracts in the pretreatment of maize stover for ruminant production
(2013) Siamba, Donald N.; Simbaya, J.; Kuria, DM.
It is increasingly understood that 1 st-generation biofuels (produced primarily from food crops such as grains, sugar beet and oil seeds) are limited in their ability to achieve targets for oil-product substitution, climate change mitigation, and economic growth. Their sustainable production is under review, as is the possibility of creating undue competition for land and water used for food and fibre production. A possible exception that appears to meet many of the acceptable criteria is ethanol produced from sugar cane. The cumulative impacts of these concerns have increased the interest in developing biofuels produced from non-food biomass. Feedstocks from ligno-cellulosic materials include cereal straw, bagasse, forest residues, and purpose-grown energy crops such as vegetative grasses and short rotation forests. These “2nd-generation biofuels” could avoid many of the concerns facing 1stgeneration biofuels and potentially offer greater cost reduction potential in the longer term. This report looks at the technical challenges facing 2nd-generation biofuels, evaluates their costs and examines related current policies to support their development and deployment. The potential for production of more advanced biofuels is also discussed. Although significant progress continues to be made to overcome the technical and economic challenges, 2nd-generation biofuels still face major constraints to their commercial deployment. Policy recommendations are given as to how these constraints might best be overcome in the future.