MacCarthy et al., 2018. Assessment of Greenhouse Gas Emissions from Different Land-Use Systems: A Case Study of CO2 in the Southern Zone of Ghana

Dilys Sefakor MacCarthy, Robert B. Zougmoré, Pierre Bienvenu Irénikatché Akponikpè, Eric Koomson, Patrice Savadogo, and Samuel Godfried Kwasi Adiku, “Assessment of Greenhouse Gas Emissions from Different Land-Use Systems: A Case Study of CO2 in the Southern Zone of Ghana,” Applied and Environmental Soil Science, vol. 2018, Article ID 1057242, 12 pages, 2018. doi:10.1155/2018/1057242

Abstract

The emission of greenhouse gases (GHGs) results in global warming and climate change. The extent to which developing countries contribute to GHG emissions is not well known. This study reports findings on the effects of different land-use systems on GHG emissions (CO2 in this case) from two locations in the southern zone of Ghana, West Africa. Site one (located at Kpong) contained a heavy clay soil while site two (located at Legon) contained a light-textured sandy soil. Land-use systems include cattle kraals, natural forests, cultivated maize fields, and rice paddy fields at site one, and natural forest, woodlots, and cultivated soya bean fields at site two. CO2 emissions were measured using the gas entrapment method (PVC chambers). Trapping solutions were changed every 12–48 h and measurement lasted 9 to 15 days depending on the site. We found that, for the same land-use, CO2 emissions were higher on the clay soil (Kpong) than the sandy soil (Legon). In the clay soil environment, the highest average CO2 emission was observed from the cattle kraal (256.7 mg·m−2·h−1), followed by the forest (146.0 mg·m−2·h−1) and rice paddy (140.6 mg·m−2·h−1) field. The lowest average emission was observed for maize cropped land (112.0 mg·m−2·h−1). In the sandy soil environment, the highest average CO2 emission was observed from soya cropped land (52.5 mg·m−2·h−1), followed by the forest (47.4 mg·m−2·h−1) and woodlot (33.7 mg·m−2·h−1). Several factors influenced CO2 emissions from the different land-use systems. These include the inherent properties of the soils such as texture, temperature, and moisture content, which influenced CO2 production through their effect on soil microbial activity and root respiration. Practices that reduce CO2 emissions are likely to promote carbon sequestration, which will consequently maintain or increase crop productivity and thereby improve global or regional food security.

Ngwabie et al., 2018. Quantifying greenhouse gas emissions from municipal solid waste dumpsites in Cameroon

Ngwabie, N.M., Wirlen, Y.L., Yinda, G.S., VanderZaag, A.C., 2018. Quantifying greenhouse gas emissions from municipal solid waste dumpsites in Cameroon. Waste Management. https://doi.org/10.1016/j.wasman.2018.02.048

Abstract

Open dumpsites that receive municipal solid waste are potentially significant sources of greenhouse gas (GHG) emissions into the atmosphere. There is little data available on emissions from these sources, especially in the unique climate and management of central Africa. This research aimed at quantifying CH4, N2O and CO2 emissions from two open dumpsites in Cameroon, located in Mussaka-Buea, regional headquarters of the South West Region and in Mbellewa-Bamenda, regional headquarters of the North West Region. Emissions were measured during the wet season (May 2015 and August 2016) at the Mussaka and Mbellewa dumpsites respectively. Dumpsite surfaces were partitioned into several zones for emission measurements, based on the current activity and the age of the waste. Static flux chambers were used to quantify gas emission rates thrice a day (mornings, afternoons and evenings). Average emissions were 96.80 ± 144 mg CH4 m−2 min−1, 0.20 ± 0.43 mg N2O m−2 min−1and 224.78 ± 312 mg CO2 m−2 min−1 in the Mussaka dumpsite, and 213.44 ± 419 mg CH4 m−2 min−1, 0.15 ± 0.15 mg N2O m−2 min−1 and 1103.82 ± 1194 mg CO2 m−2 min−1 at the Mbellewa dumpsite. Emissions as high as 1784 mg CH4 m−2 min−1, 2.3 mg N2O m−2 min−1 and 5448 mg CO2m−2 min−1 were measured from both dumpsites. Huge variations observed in emissions between the different zones on the waste surface were likely a result of the heterogeneous nature of the waste, different stages in waste decomposition and different environmental conditions within the waste. Management activities that disturb waste, such as spreading and compressing potentially increase gas emissions, while covering waste with a layer of soil potentially mitigate gas emissions. Recommendations were for dumpsites to be upgraded to sanitary landfills, and biogas production from such landfills should be exploited to reduce CH4 emissions.

Gütlein et al., 2018. Impacts of climate and land use on N2O and CH4 fluxes from tropical ecosystems in the Mt. Kilimanjaro region, Tanzania

Gütlein, A., Gerschlauer, F., Kikoti, I., Kiese, R., 2018. Impacts of climate and land use on N2O and CH4 fluxes from tropical ecosystems in the Mt. Kilimanjaro region, Tanzania. Global Change Biology 24, 1239-1255.

Abstract

In this study, we quantify the impacts of climate and land use on soil N2O and CH4 fluxes from tropical forest, agroforest, arable and savanna ecosystems in Africa. To do so, we measured greenhouse gases (GHG) fluxes from 12 different ecosystems along climate and land‐use gradients at Mt. Kilimanjaro, combining long‐term in situ chamber and laboratory soil core incubation techniques. Both methods showed similar patterns of GHG exchange. Although there were distinct differences from ecosystem to ecosystem, soils generally functioned as net sources and sinks for N2O and CH4 respectively. N2O emissions correlated positively with soil moisture and total soil nitrogen content. CH4 uptake rates correlated negatively with soil moisture and clay content and positively with SOC. Due to moderate soil moisture contents and the dominance of nitrification in soil N turnover, N2O emissions of tropical montane forests were generally low (<1.2 kg N ha−1 year−1), and it is likely that ecosystem N losses are driven instead by nitrate leaching (~10 kg N ha−1 year−1). Forest soils with well‐aerated litter layers were a significant sink for atmospheric CH4 (up to 4 kg C ha−1 year−1) regardless of low mean annual temperatures at higher elevations. Land‐use intensification significantly increased the soil N2O source strength and significantly decreased the soil CH4 sink. Compared to decreases in aboveground and belowground carbon stocks enhanced soil non‐CO2 GHG emissions following land‐use conversion from tropical forests to homegardens and coffee plantations were only a small factor in the total GHG budget. However, due to lower ecosystem carbon stock changes, enhanced N2O emissions significantly contributed to total GHG emissions following conversion of savanna into grassland and particularly maize. Overall, we found that the protection and sustainable management of aboveground and belowground carbon and nitrogen stocks of agroforestry and arable systems is most crucial for mitigating GHG emissions from land‐use change.

Majiwa et al., 2018. Increasing agricultural productivity while reducing greenhouse gas emissions in sub-Saharan Africa: myth or reality?

Majiwa, E., Lee, B.L., Wilson, C., 2018. Increasing agricultural productivity while reducing greenhouse gas emissions in sub-Saharan Africa: myth or reality? Agricultural Economics 49, 183-192.

Abstract

The motivation for this study stems from two major concerns that are interlinked. The first is the decades long food insecurity crisis faced by sub‐Saharan African (SSA) countries which is still prevalent. The second is the negative impact greenhouse gas (GHG) emissions from agriculture may have on future food production and which is likely to worsen the food insecurity problem. The conundrum SSA farmers face is how to increase food output through productivity growth while minimizing GHG emissions. To measure changes in productivity growth and GHG emissions, this study evaluates the agricultural performance of 18 SSA countries by utilizing the Malmquist–Luenberger index to incorporate good and bad outputs for the years 1980–2012. The empirical evidence demonstrates that productivity is overestimated when bad outputs are not considered in the production model. The analysis provides a better understanding of the effectiveness of previous mitigation methods and which informs an appropriate course of action needed to achieve the twin objectives of increasing agriculture productivity while reducing GHG emissions.

Hickman et al., 2017. Nonlinear response of nitric oxide fluxes to fertilizer inputs and the impacts of agricultural intensification on tropospheric ozone pollution in Kenya

Hickman, J.E., Huang, Y., Wu, S., Diru, W., Groffman, P.M., Tully, K.L., Palm, C.A., 2017. Nonlinear response of nitric oxide fluxes to fertilizer inputs and the impacts of agricultural intensification on tropospheric ozone pollution in Kenya. Global Change Biology 23, 3193-3204.

Abstract

Crop yields in sub‐Saharan Africa remain stagnant at 1 ton ha−1, and 260 million people lack access to adequate food resources. Order‐of‐magnitude increases in fertilizer use are seen as a critical step in attaining food security. This increase represents an unprecedented input of nitrogen (N) to African ecosystems and will likely be accompanied by increased soil emissions of nitric oxide (NO). NO is a precursor to tropospheric ozone, an air pollutant and greenhouse gas. Emissions of NO from soils occur primarily during denitrification and nitrification, and N input rates are a key determinant of emission rates. We established experimental maize plots in western Kenya to allow us to quantify the response function relating NO flux to N input rate during the main 2011 and 2012 growing seasons. NO emissions followed a sigmoid response to fertilizer inputs and have emission factors under 1% for the roughly two‐month measurement period in each year, although linear and step relationships could not be excluded in 2011. At fertilization rates above 100 kg N ha−1, NO emissions increased without a concomitant increase in yields. We used the geos‐chem chemical transport model to evaluate local impacts of increased NO emissions on tropospheric ozone concentrations. Mean 4‐hour afternoon tropospheric ozone concentrations in Western Kenya increased by up to roughly 2.63 ppbv under fertilization rates of 150 kg N ha−1or higher. Using AOT40, a metric for assessing crop damage from ozone, we find that the increased ozone concentrations result in an increase in AOT40 exposure of approximately 110 ppbh for inputs of 150 kg N ha−1 during the March–April–May crop growing season, compared with unfertilized simulations, with negligible impacts on crop productivity. Our results suggest that it may be possible to manage Kenyan agricultural systems for high yields while avoiding substantial impacts on air quality.

Ortiz-Gonzalo et al., 2018. Multi-scale measurements show limited soil greenhouse gas emissions in Kenyan smallholder coffee-dairy systems.

Ortiz-Gonzalo, D., de Neergaard, A., Vaast, P., Su찼rez-Villanueva, V., Oelofse, M., Rosenstock, T.S., 2018. Multi-scale measurements show limited soil greenhouse gas emissions in Kenyan smallholder coffee-dairy systems. Science of the Total Environment 626, 328-339.

Abstract

Efforts have been made in recent years to improve knowledge about soil greenhouse gas (GHG) fluxes from sub-Saharan Africa. However, data on soil GHG emissions from smallholder coffee-dairy systems have not hitherto been measured experimentally. This study aimed to quantify soil GHG emissions at different spatial and temporal scales in smallholder coffee-dairy farms in Murang'a County, Central Kenya. GHG measurements were carried out for one year, comprising two cropping seasons, using vented static chambers and gas chromatography. Sixty rectangular frames were installed on two farms comprising the three main cropping systems found in the area: 1) coffee (Coffea arabica L.); 2) Napier grass (Pennisetum purpureum); and 3) maize intercropped with beans (Zea mays and Phaseolus vulgaris). Within these fields, chambers were allocated on fertilised and unfertilised locations to capture spatial variability. Cumulative annual fluxes in coffee plots ranged from 1 to 1.9 kg N2O-N ha− 1, 6.5 to 7.6 Mg CO2-C ha− 1 and − 3.4 to − 2.2 kg CH4 -C ha− 1, with 66% to 94% of annual GHG fluxes occurring during rainy seasons. Across the farm plots, coffee received most of the N inputs and had 56% to 89% higher emissions of N2O than Napier grass, maize and beans. Within farm plots, two to six times higher emissions were found in fertilised hotspots – around the perimeter of coffee trees or within planted maize rows – than in unfertilised locations between trees, rows and planting holes. Background and induced soil N2O emissions from fertiliser and manure applications in the three cropping systems were lower than hypothesized from previous studies and empirical models. This study supplements methods and underlying data for the quantification of GHG emissions at multiple spatial and temporal scales in tropical, smallholder farming systems. Advances towards overcoming the dearth of data will facilitate the understanding of synergies and tradeoffs of climate-smart approaches for low emissions development.

Graphical abstract

Pryor et al., 2017. Impact of agricultural practices on energy use and greenhouse gas emissions for South African sugarcane production.

Pryor, S.W., Smithers, J., Lyne, P., van Antwerpen, R., 2017. Impact of agricultural practices on energy use and greenhouse gas emissions for South African sugarcane production. Journal of Cleaner Production 141, 137-145.

Abstract

The environmental footprint of agricultural production can vary significantly both between countries and within a country based on regional conditions and agricultural practices. A life cycle assessment approach was used to model primary fossil fuel energy inputs and greenhouse gas emissions associated with the production of sugarcane in South Africa. Results were calculated for sugarcane produced in two distinct regions, the irrigated North and the non-irrigated North Coast. Regional differences also include terrain, soil, and use of mechanization. Models were adapted to estimate the impacts of burning prior to harvest, leaving a biomass mulch blanket with green cane harvesting, and increasing the level of mechanization for harvest and other field operations. Irrigation contributes to a higher energy input in the irrigated North but differences are mitigated by the lower fertilizer, agro-chemical, and diesel use per ton of sugarcane produced there. Despite higher energy inputs in the irrigated North, greenhouse gas emissions are similar for sugarcane produced in each region. Green cane harvesting reduces energy inputs and greenhouse gas emissions by 4% and 16%, respectively, in both regions. Impacts of mechanization on soil compaction and stool damage result in lower yields and proportionally higher energy inputs and greenhouse gas emissions. Results demonstrate the potential for variability in LCA results based on regional differences in production practices within a country.