Potential environmental impact of bromoform from Asparagopsis farming in Australia

To mitigate the rumen enteric methane (CH4) produced by ruminant livestock, Asparagopsis taxiformis is proposed as an additive to ruminant feed. During the cultivation of Asparagopsis taxiformis in the sea or in terrestrial based systems, this macroalgae, like most seaweeds and phytoplankton, produces a large amount of bromoform (CHBr3), which may contribute to ozone depletion once released into the atmosphere. In this study, the impact of CHBr3 on the stratospheric ozone layer resulting from potential emissions from proposed Asparagopsis cultivation in Australia is assessed by weighting the emissions of CHBr3 with the ozone depletion potential (ODP), which is traditionally defined for long-lived halogens but has been also applied to very short lived substances (VSLSs). An annual yield of ~3.5 × 104 Mg dry weight (DW) is required to meet the needs of 50 % of the beef feedlot and dairy cattle in Australia. Our study shows that the intensity and impact of CHBr3 emissions varies dependent on location and cultivation scenarios. Of the proposed locations, tropical farms near the Darwin region are associated with largest CHBr3 ODP values. However, farming of Asparagopsis using either ocean or terrestrial cultivation systems at any of the proposed locations does not have potential to impact the ozone layer. Even if all Asparagopsis farming was performed in Darwin, the emitted CHBr3 would amount to less than 0.016 % of the global ODP-weighted emissions. The remains are relatively small even if the intended annual yield in Darwin is scaled by a factor 30 to meet the global requirements, which will increase the global ODP-weighted emissions by 0.48 %

Life cycle assessment of expanded polystyrene

Expanded polystyrene (EPS) is one of the most common materials used in packaging. In Malaysia, EPS is a type of plastic which is not in the recycling category. Usually, EPS wastes will end up in landfill and incinerator, leading to severe environmental impacts. Therefore, a cradle-to-grave life cycle assessment (LCA) study of EPS was carried out to investigate the potential environmental impacts of EPS. The most significant potential environmental impact will also be identified. Both will be identified under 2 different scenarios. The study was analyzed using GaBi Education Software with the method of TRACI 2.1 to the environmental indicators of global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), and ozone depletion potential (ODP). In scenario 1, the emission percentage for GWP, AP, EP, and ODP are 99.73 %, 0.21 %, 0.06 %, and 3x10-6 %, respectively. As for scenario 2, all the 3 conditions show similar trend with scenario 1. The LCA study of EPS is particularly focused on the manufacturing, distribution, and the end-of-lifetime treatments, with the introduction of recycling into the system. The findings show that manufacturing of EPS is the major contributor of the environmental impacts and GWP contributes to the most significant potential environmental impacts. Overall, recycling was found to have the least impact to the environment, which possibly be used as the new end-of-lifetime treatment of EPS in Malaysia.

Environmental Life Cycle Assessment of Ammonia-Based Electricity

In recent years, several researchers have studied the potential use of ammonia (NH3) as an energy vector, focused on the techno-economic advantages and challenges for full global deployment. The use of ammonia as fuel is seen as a strategy to support decarbonization; however, to confirm the sustainability of the shift to ammonia as fuel in thermal engines, a study of the environmental profile is needed. This paper aims to assess the environmental life cycle impacts of ammonia-based electricity generated in a combined heat and power cycle for different ammonia production pathways. A cradle-to-gate assessment was developed for both ammonia production and ammonia-based electricity generation. The results show that electrolysis-based ammonia from renewable and nuclear energy have a better profile in terms of global warming potential (0.09–0.70 t CO2-eq/t NH3), fossil depletion potential (3.62–213.56 kg oil-eq/t NH3), and ozone depletion potential (0.001–0.082 g CFC-11-eq/t NH3). In addition, surplus heat for district or industrial applications offsets some of the environmental burden, such as a more than 29% reduction in carbon footprint. In general, ammonia-based combined heat and power production presents a favorable environmental profile, for example, the carbon footprint ranges from −0.480 to 0.003 kg CO2-eq/kWh.

Targeted knockout of the gene OsHOL1 removes methyl iodide emissions from rice plants

Iodine deficiency represents a public health problem worldwide. To increase the amount of iodine in the diet, biofortification strategies of plants have been tried. They rely on the exogenous administration of iodine to increase its absorption and accumulation. However, iodine is not stable in plants and can be volatilized as methyl iodide through the action of specific methyltransferases encoded by the HARMLESS TO OZONE LAYER (HOL) genes. The release of methyl iodide in the atmosphere represents a threat for the environment due to its ozone depletion potential. Rice paddies are among the strongest producers of methyl iodide. Thus, the agronomic approach of iodine biofortification is not appropriate for this crop, leading to further increases of iodine emissions. In this work, we used the genome editing CRISPR/Cas9 technology to knockout the rice HOL genes and investigate their function. OsHOL1 resulted a major player in methyl iodide production, since its knockout abolished the process. Moreover, its overexpression reinforced it. Conversely, knockout of OsHOL2 did not produce effects. Our experiments helped elucidating the function of the rice HOL genes, providing tools to develop new rice varieties with reduced iodine emissions and thus more suitable for biofortification programs without further impacting on the environment.

New Refrigerant Molecules from Structure Optimization

In the present work, various objective functions were formulated and optimized using the mixed integer nonlinear programming and the generalized reduced gradient nonlinear method from the solver tool of Microsoft® Excel 2016, respectively. The CH3FO2, C2H4F2O, CH2F2O2, CH2F2O, C3H4F2, and the C2H2F2O molecules were found to meet structural feasibility constraints and physical properties from refrigerant molecules and have not previously been reported in the literature. These new refrigerants present global warming potential values similar to that from the R-134a and Freon 12 refrigerants and null ozone depletion potential. Moreover, these molecules are normally flammable, as similar as to R-134a refrigerant. The CH3FO2, C2H4F2O, CH2F2O2, C2H2F2O, and CH2F2O show toxicity values similar to R-134a and Freon 12 refrigerants.

A Prototype Of Propane Refrigerant Based ASHP With Heat Recovery Ventilation (HRV) System

In recent years, an increased focus has been given to replacing high Global Warming Potential (GWP) refrigerants with relatively low GWP alternatives. Energy efficiency, carbon reduction and HFC phase-down will push the heat pump market towards natural refrigerants. Propane (R-290) is a type of hydrocarbon refrigerant with zero ozone depletion potential and very low GWP (< 4). R-290 is a pure refrigerant and has excellent thermodynamic properties. The research presented in this project is a study of the refrigerant side of an ASHP to analyze the thermodynamic performance of the propane refrigerant under different operating conditions. For this purpose, a test rig was designed and constructed in a single packaged air source heat pump unit. In addition, the air side of the tested heat pump was designed for energy recovery in cooling and heating modes. The compactness of the system and installation of air dampers allows its placement for coupling to the building renewable air sources, such as a building integrated photovoltaic/thermal (BIPV/T) system.

A Prototype Of Propane Refrigerant Based ASHP With Heat Recovery Ventilation (HRV) System

In recent years, an increased focus has been given to replacing high Global Warming Potential (GWP) refrigerants with relatively low GWP alternatives. Energy efficiency, carbon reduction and HFC phase-down will push the heat pump market towards natural refrigerants. Propane (R-290) is a type of hydrocarbon refrigerant with zero ozone depletion potential and very low GWP (< 4). R-290 is a pure refrigerant and has excellent thermodynamic properties. The research presented in this project is a study of the refrigerant side of an ASHP to analyze the thermodynamic performance of the propane refrigerant under different operating conditions. For this purpose, a test rig was designed and constructed in a single packaged air source heat pump unit. In addition, the air side of the tested heat pump was designed for energy recovery in cooling and heating modes. The compactness of the system and installation of air dampers allows its placement for coupling to the building renewable air sources, such as a building integrated photovoltaic/thermal (BIPV/T) system.

Performance Evaluation of a Split Unit Air-Conditioner Retrofitted with Hydrocarbon Refrigerant (HC22)

The performance evaluation of a small capacity split unit air-conditioner when retrofitted with hydrocarbon refrigerant (HC22) was presented in this paper. Unlike traditional hydrofluorocarbon refrigerant (HCFC22) which possess ozone depletion potential (ODP) and high global warming potential (GWP), the HC22 refrigerant has zero ODP and a GWP value less than 3. Experimental work was carried out in a controlled environment which mimics an office room, with surrounding temperature varied from 25°C, 30°C and 35°C to simulate the typical cooling loads in Malaysia. The performance of HC22 refrigerant was compared with that of HCFC22 at these temperatures. The results show that the coefficient of performance (COP) of HC22 is higher, ranging from 3.5% to about 11% in comparison to HC22. The observation during experiments also shows that a typical HCFC22 can be retrofitted without any issue. The COP values obtained were 6.03, 6.35 and 6.15 for HC22 and 5.71, 5.66 and 5.63 for HCFC22 respectively. It can be concluded from this study that HC22 can be retrofitted directly to a HCFC system but other issues such as refrigerant flammability and safety issues shall be taken into account.

Experimental investigation of cop for an air conditioner using zeotropic blend

In this project an air conditioner was fabricated using R-410a as refrigerant and its COP is calculated. CFCs have been phased out, except for essential users, and HCFCs are to be eliminated by 2020, because of their ozone depletion potential.This generates a need for the investigation of zero ozone depletion potential (ODP) refrigerants or refrigerant blends.R410A is among newer brand of refrigerant blend, with zero ODP. The biggest difference to R22 is the pressure levels generated which are more than50% higher. The refrigerant R410A operates at higher pressure at the same saturated temperatures than R22, therefore system should be re designed. The overall COP of the system is 5 to 6% more than the R22. We also calculated the relative humidity of room air after it gets cooled, heat removed from the air by considering the input data from weather online which provides us the day to day climatic conditions. Present work provides us regarding performance of an self fabricated zeotropic air conditioner.

Comparative evaluation of a two-stage refrigeration system with flash intercooling using different refrigerants

The aim of this study is to investigate the effect of low global warming potential refrigerants on the optimum intermediate pressure (POPT,int) and performance (COP) values of a refrigeration system with flash intercooling. For realize, the optimum operating parameters of system were determined in low temperature applications through a theoretical analysis according to the different refrigerants (R290, R404A, R407C, R507A, and R22). The theoretical modelling of system is done by optimizing the intermediate pressure at given evaporation (TE) and condensation (TC) temperatures for selected refrigerants. After optimization, the maximized values of COP and Second law efficiency are computed from the predicted values of POPT,int . The linear regression method is then used to derive three correlations of POPT,int , maximum values of COP and Second law efficiency according to TE and TC. Hence, the POPT,int values maximizing the system performance are found from various TE and TC values for each refrigerant. Due to calculations, increasing TE and TC cause the increase in POPT,int in low temperature applications. The R507A system has the highest POPT,int values and R22 system has the lowest POPT?int values. Although R22 system has slightly more efficient than R290 system, it is being phased out world?wide because of the risk of ozone depletion potential and global warming potential considerations. Therefore, it is important to evaluate the R22 replacement options. The R290 was discovered to have better performance than the R404A, R407C and R507A systems in terms of COPmax (1.81), global warming potential (11), and ozone depletion potential (0) when TE and TC are -35?C and 40?C.