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The key factor in sustainable biogas production is a feedstock whose production has no adverse impact on the environment. Since maize cultivation harms the environment, biogas plant operators seek a more sustainable feedstock. Common reed is an invasive species mown as part of wetland conservation measures, or it can be harvested from paludiculture. This study aimed to investigate wet co-digestion of maize silage with 10%, 30%, and 50% content of common reed silage using the biochemical methane potential (BMP) test. In addition, the potential energy generated and avoided greenhouse gas (GHG) emissions were calculated. The substitution of maize silage with 10%, 30%, and 50% content of reed silage reduced the methane (CH4) yield by 13%, 28%, and 35%, respectively. A disadvantage of reed silage addition was increased ammonia (NH3) and hydrogen sulfide (H2S) concentrations in biogas. Although substituting maize silage with reed silage decreases the CH4 yield, the co-digestion of maize and reed biomass from conservation or paludiculture may positively affect environmental aspects of energy generation. The substitution of maize with reed in biogas plants decreases the area used for maize cultivation and reduces GHG emissions.

Economic criteria have prevailed in studies on integration of renewable energies. Tons of dangerous emissions are emitted by a biomass fuel, causing negative impacts over atmosphere and health. Current research proposes Pinch Analysis of solar thermal energy and the joint use of biomass (sugarcane bagasse) to produce heat and power in a Caribbean sugar mill; measuring emissions like: carbon oxide CO, carbon dioxide CO2, dinitrogen monoxide N2O, nitrogen oxides NOx, sulfur oxides SOx, non-methane volatile organic compounds NMVOC, methane CH4, and particulate matters, to have a global and clear view of the impacts of biomass as a renewable fuel. Variables like kWh cost, the installation and device area of renewable energy, and greenhouse gas emissions, are analysed to assess the effect on the integration final design, the target of which is to control the use of biomass. It is possible to produce an economically competitive integration design of solar system LCOEth solar = 0.0636 USD/kWh, LCOEele = 0.1392 USD/kWh), zero greenhouse gases emissions (ΔTminrew=7 °C), and deletion of 378,711.53 t/year of CO2 and 9567.56 t/year of solid particles. There are many possibilities that can implemented; in one of them, bagasse burning is reduced by 30% and the solar collector network for required power production is reduced by 68%.

Modernisation of municipal and industrial wastewater treatment plants (WWTPs) should be carried out, taking into account its impact on global warming, e.g., through carbon footprint (CF) analysis. An important industrial sector in Poland is the dairy industry. In dairy WWTPs, the aerobic sewage sludge stabilisation applied thus far is being replaced by the anaerobic process. This change is positive due to the possibility of energy production, but it is unclear how it affects greenhouse gases (GHG) emissions. The aim of the research was to perform CF analysis for two scenarios of dairy WWTP operation. The analysis was based on the real operating data of the current system (current scenario) and project of its modernisation (alternative scenario). The current scenario consists of mechanical and dissolved air flotation (DAF) treatment, biological treatment in sequence batch reactors (SBRs), aerobic sewage sludge stabilisation and its final farmland usage. The alternative scenario assumes replacing aerobic stabilisation with anaerobic stabilisation and a combined heat and power (CHP) system. The CF calculations were based on empirical models, taking into account different emission input parameters, expressed in CO2 equivalents (CO2e). The total CF of the current scenario was 22 kg CO2e PE−1 year−1, while the alternative was 45 kg CO2e PE−1 year−1. The largest share in the current scenario belongs to emissions from WWTPs and energy use, while in the alternative, there is the addition of emissions from biogas use.

This study analyzes the road freight sector of São Paulo state to identify the best options to reduce greenhouse gases emissions and local pollutants, such as particulate matter, nitrogen oxides, carbon monoxide, and hydrocarbons. Additionally, the investment cost of each vehicle is also analyzed. Results show that electric options, including hybrid, battery, and hydrogen fuel-cell electric vehicles represent the best options to reduce pollutants and greenhouse gases emissions concomitantly, but considerable barriers for their deployment are still in place. With little long-term planning on the state level, electrification of the transport system, in combination with increased renewable electricity generation, would require considerable financial support to achieve the desired emissions reductions without increasing energy insecurity.

The economic structure of a city evolves as the city develops, resulting in a change in energy consumption. This paper presents a historical review of Hong Kong’s economic development and energy consumption from 1970 to 2015. Based on the official data from the Hong Kong government, it was found that Hong Kong’s gross domestic product increased from HKD 208 billion in 1970 to HKD 2398 billion in 2015 in which the contribution from the manufacturing sector peaked in 1985. Energy consumption increased by 9.3 times from 140.2 PJ in 1970 (mostly oil products) to 1298.2 PJ (including oil products, natural gas, coal, and imported electricity) in 2015. The greenhouse gas (GHG) emissions due to energy consumption were determined based on emission factors for different fuels. Results show that GHG emissions increased from 10.7 million tons (Mt) of CO2-equivalent in 1970 to 99.1 Mt of CO2-equivalent in 2015.