Eggshells – assisted hydrolysis of banana pulp for biogas production

In this study, pretreatment of banana pulp using eggshells in both calcined and un-calcined forms to examine the extent of hydrolysis was conducted. Reactor CO containing banana pulp and inoculum but with no eggshells added was used as the control, while reactors C1, C2, C3, C4, and C5 containing banana pulp and inoculum were spiked with 1, 3, 5, 7, and 9 g of un-calcined  eggshells and calcined eggshells, for experiment 1 and 2, respectively. Anaerobic digestion was carried out at mesophilic  temperature (35°C) for a period of 20 days. Digester C3 with 5 g of calcined eggshells gave the largest cumulative biogas yield of 2343 mL with 62% CH4, follow. The least biogas yield of 10 mL was obtained in digester C5with 9 g of calcined eggshells additive.Key words: Anaerobic digestion, banana pulp hydrolysis biogas, eggshells

Farming systems and soil fertility management practices in smallholdings on the southern slopes of Mount Kilimanjaro, Tanzania

In the northern part of Tanzania, the slopes of Mount (Mt.) Kilimanjaro are the most important areas, both in terms of socio-economic development and ecological succession. The main agricultural systems in the area are banana-based (in the highlands) and maize-based (in the lowlands), with strong interlinkage between them via residual transfer from the lowlands to the mountains. This study assessed the soil fertility status between the two contrasting farming areas of highland and lowland farms in Hai district along the slopes of Mt. Kilimanjaro. To achieve this, smallholder farmers along the slope [from above 1000 meters above sea level (m.a.s.l) banana-based down to maize-based, i.e., less than 1000 m.a.s.l] who practice crop residual transfer from maize-based to banana-based farming systems were selected. Qualitative information regarding the demographics, farming practices, and soil fertility management in the two areas were gathered using a semi-structured questionnaire. Soils from both areas (highland and lowland farms) were collected and analyzed in the laboratory for the key soil properties. The demographic results show that agriculture is mostly done by adults and elders (>40 years old). Manure was most commonly reported to be used in the highlands, while inorganic fertilizers were mainly used in lowland areas. The major challenges for soil fertility management are a shortage of manure and high cost of inorganic fertilizers. The results of soil nutrients revealed that lowland zones (>1000 m.a.s.l) had significantly (p< 0.01) lower levels of nitrogen (0.14%) and organic carbon (OC) (1.22%) compared with highland zones. Extractable phosphorus (P) was significantly lower in both the highland and lowland zones, at 9.3 mg kg-1 and 8.2 mg kg-1, respectively, compared with other nutrients. However, potassium (K+) was significantly (p<0.01) lower [0.34 cmol (+) kg-1] in the highland zone compared to lowland areas. The data show that there is a severe depletion of soil nutrients in the lowland area of Hai district. Notwithstanding the efforts of the small-holder farmers; the study comes to the conclusion that increasing agricultural yield and the sustainability of farming systems require replenishing the nutrients in the soil along the slope of Mount Kilimanjaro

Where does land use matter most? Contrasting land use effects on river quality at different spatial scales

Understanding the influence of land-use activities on river quality has been a key focus of river monitoring programs worldwide. However, defining which land-use spatial scale is relevant remains elusive. In this study, therefore, we contrasted the influence of land use on river quality using three types of land-use estimators, namely circular buffers around a monitoring site, circular buffers upstream of the monitoring site and the entire watershed area upstream of the monitoring site. The land-use percentage compositions within the Usa-Kikuletwa River catchment in northeastern Tanzania were quantified using Landsat-8 satellite images with a maximum mapping resolution of 30 m. Redundancy analysis models and generalized linear models were used to evaluate the influence of land use on macroinvertebrate assemblages and physico-chemical water quality at different spatial scales in the dry and wet seasons. Overall, a substantial fraction of variation in physico-chemical water quality, macroinvertebrate taxon richness, Chao-1 and TARISS (Tanzania River Scoring System) score could be explained by land use of the entire watershed area upstream of the monitoring site in the dry and wet seasons. However, macroinvertebrate abundances showed strong links with more local land-use patterns within 100 m and 2 km radii. Circular buffers upstream of monitoring sites were more informative for macroinvertebrate assemblages than circular buffers around the monitoring sites. However, the latter did correlate well with physico-chemical water quality variables. Land-use variables correlated across spatial scales (i.e., 100 m up to 2 km radii), but not with the land use in the entire watershed area above the monitoring site. Our results indicate that physico-chemical water quality variables and macroinvertebrates may respond differently to land-uses at different scales. More importantly, our results illustrate that the choice regarding spatial land-use metrics can bias conclusions of environmental impact studies in river systems.status: publishe

Where does land use matter most? Contrasting land use effects on river quality at different spatial scales

Understanding the influence of land-use activities on river quality has been a key focus of river monitoring programs worldwide. However, defining which land-use spatial scale is relevant remains elusive. In this study, therefore, we contrasted the influence of land use on river quality using three types of land-use estimators, namely circular buffers around a monitoring site, circular buffers upstream of the monitoring site and the entire watershed area upstream of the monitoring site. The land-use percentage compositions within the Usa-Kikuletwa River catchment in northeastern Tanzania were quantified using Landsat-8 satellite images with a maximum mapping resolution of 30 m. Redundancy analysis models and generalized linear models were used to evaluate the influence of land use on macroinvertebrate assemblages and physico-chemical water quality at different spatial scales in the dry and wet seasons. Overall, a substantial fraction of variation in physico-chemical water quality, macroinvertebrate taxon richness, Chao-1 and TARISS (Tanzania River Scoring System) score could be explained by land use of the entire watershed area upstream of the monitoring site in the dry and wet seasons. However, macroinvertebrate abundances showed strong links with more local land-use patterns within 100 m and 2 km radii. Circular buffers upstream of monitoring sites were more informative for macroinvertebrate assemblages than circular buffers around the monitoring sites. However, the latter did correlate well with physico-chemical water quality variables. Land-use variables correlated across spatial scales (i.e., 100 m up to 2 km radii), but not with the land use in the entire watershed area above the monitoring site. Our results indicate that physico-chemical water quality variables and macroinvertebrates may respond differently to land-uses at different scales. More importantly, our results illustrate that the choice regarding spatial land-use metrics can bias conclusions of environmental impact studies in river system