Sustainable waste-to-energy development in Malaysia: Appraisal of environmental, financial, and public issues related with energy recovery from municipal solid waste

As Malaysia is a fast-developing country, its prospects of sustainable energy generation are at the center of debate. Malaysian municipal solid waste (MSW) is projected to have a 3.3% increase in annual generation rate at the same time an increase of 3.3% for electricity demand. In Malaysia, most of the landfills are open dumpsite and 89% of the collected MSW end up in landfills. Furthermore, huge attention is being focused on converting MSW into energy due to the enormous amount of daily MSW being generated. Sanitary landfill to capture methane from waste landfill gas (LFG) and incineration in a combined heat and power plant (CHP) are common MSW-to-energy technologies in Malaysia. MSW in Malaysia contains 45% organic fraction thus landfill contributes as a potential LFG source. Waste-to-energy (WTE) technologies in treating MSW potentially provide an attractive economic investment since its feedstock (MSW) is collected almost for free. At present, there are considerable issues in WTE technologies although the technology employing MSW as feedstock are well established, for instance the fluctuation of MSW composition and the complexity in treatment facilities with its pollutant emissions. Thus, this study discusses various WTE technologies in Malaysia by considering the energy potentials from all existing incineration plants and landfill sites as an effective MSW management in Malaysia. Furthermore, to promote local innovation and technology development and to ensure successful long-term sustainable economic viability, social inclusiveness, and environmental sustainability in Malaysia, the four faculties of sustainable development namely technical, economic, environmental, and social issues affiliated with MSW-to-Energy technologies were compared and evaluated

Ancillary palm oil fuel ash (POFA) in sequencing batch reactor for enhancing recalcitrant pollutants removal from domestic wastewater

Domestic wastewater has been generated massively along with rapid growth of population and economic. Biological treatment using sequencing batch reactor (SBR) augmented with palm oil fuel ash (POFA) was investigated for the first time. The performance of POFA in enhancing biological treatment of wastewater has not been tested. The porosity property of POFA can improve SBR efficiency by promoting growth of mixed liquor suspended solids (MLSS) and formation of larger flocs for settling and facilitating attachment of microorganisms and pollutants onto POFA surfaces. The properties of POFA were tested to identify morphological properties, particle size, surface area, chemical compositions. Four SBRs, namely SBR1, SBR2, SBR3 and SBR4 were provided with aeration rate of 1, 2, 3 and 4 L/min, respectively. Each reactor was augmented with different dosages of POFA. Optimum aeration rate and POFA concentration were identified by the performance of SBRs in removing chemical oxygen demand (COD), ammoniacal nitrogen (NH3–N) and colour from domestic wastewater. The results showed the most efficient COD (97.8%), NH3–N (99.4%) and colour (98.8%) removals were achieved at optimum POFA concentration of 4 g/L in SBR and aeration rate of 1 L/min. The study also found that higher aeration rate would contribute to the smaller specific size of flocs and decrease the pollutant removal efficiency

Advanced treatment of poultry slaughterhouse wastewater using electrocoagulation and peroxidation: Parametric analysis and process optimization

In this research, electrocoagulation-intensified peroxidation using an aluminum electrode was studied as a post-treatment method for poultry slaughterhouse wastewater (SWW) with 4 operational variables (pH, current density, contact time, and H2O2 dosage). Optimization was carried out using response surface methodology. Analysis of variance was used to analyze the experimental data, and a second-order model was created to test the effects of process parameters on treatment performance. The optimum conditions were chosen as follows: pH 5.83, 0.18 g/L H2O2 dosage, 58.60 min contact time, and current density of 4.21 mA/cm2. The compatibility of the predicted optimum conditions has been verified by experimental data. As a result of the experiments performed under optimum conditions, COD, TSS, and color removals were found to be 97.89%, 99.31%, and 98.56%, respectively. The difference between experimental and predicted values was found to be less than 0.86%. The final treated effluent met the discharge standards determined by the World Bank, EU, US, and Malaysian Department of Environment. Under optimum conditions, the cost of treating 1 cubic meter of SWW was calculated as 3.02 MYR ($ 0.68)

Microalgae cultivation in stabilized landfill leachate for simultaneous treatment and biomass production

Background: The high toxicity of landfill leachate has motivated to an investigation of economical and ecological treatment prior releasing into environment. Recently, microalgae have emerged as an alternative method due to its ability to recover nutrient and potential for bio-fuel production. However, the high concentrations of inhibitory compounds and ammoniacal nitrogen in young landfill leachates require high dilutions for microalgae to thrive. Hence, this study aims to evaluate the performance of microalgae by using stabilized landfill leachate with lower to no dilutions in nutrient removal, biomass and lipid production. Methods: Leachate concentrations of 33, 44, 66, 89 and 100 v/v% were initially treated with the microalgae C. vulgaris. Parameters of chemical oxygen demand (COD), ammoniacal nitrogen (NH3–N), orthophosphate (PO43−), total phosphorus (TP) and colour removal were evaluated. Cost analysis was conducted to evaluate the economical appropriateness. Significant findings: The highest removals were achieved at 43.67% of COD, >97% of NH3–N, 79.26% of PO43−, 77.64% of TP and 44.04% of colour. Highest biomass yield obtained was 220 mg/L by 89 v/v% of leachate concentration with 8.14% of lipid yield. Cost of treatment was calculated to be ∼$0.02 per m3 leachate. The feasibility of stabilized landfill leachate treatment without any dilutions using microalgae was attained as they can survive amidst this condition, perform nutrient removals, and produce biomass simultaneously

Insights into active and passive carbon sequestration and causticity reduction in hazardous red mud slurry

Batch experiments were conducted to collect data for obtaining insights into the chemical mechanisms and kinetics of red mud neutralization by both atmospheric (passive treatment) and injected CO2 (active treatment) in the absence and presence of gypsum. Active treatments allowed effective sequestration of CO2 within 1 h. A mixing ratio of gypsum to red mud at 0.04–0.06 enabled effective control of pH rebound, completely eliminating the causticity of the red mud by reducing the pH value of red mud to < 9. The carbonation of red mud was realized through the formation of carbon-containing minerals, mainly basic aluminium carbonates (largely dawsonite), sodium bicarbonate, sodium carbonate and calcite. The importance of calcite as a carbon carrier increased when gypsum was added. Passive treatments also allowed simultaneous causticity reduction and carbon sequestration but at a much slower rate compared to the active treatments. The research findings obtained from this study have implications for developing strategies to cost-effectively manage red mud. Where flue gas is available, active treatment could be a feasible option for simultaneously reducing the harmfulness of red mud and CO2 emission. Passive treatment can be used as a natural attenuation process for low-cost management of red mud. Where off-site utilization of red mud is feasible, gypsum addition at an optimal rate could be a more appropriate option. For future study, industrial-scale experiments are required to validate the research findings obtained from this laboratory-scale study

Optimization of self-fermented period of waste coconut endosperm destined to feed black soldier fly larvae in enhancing the lipid and protein yields

The prime objective of this study was to simultaneously enhance the lipid and protein yields from black soldier fly larvae (BSFL) fed with waste coconut endosperm. The waste coconut endosperm impoverished with nutrient content lost during milk extraction was nutritively fortified via self-fermentation process with time period ranging from 2 to 8 weeks before administering to BSFL. The results showed peak nutrient content was attained from week-4 self-fermented waste coconut endosperm. Using this feed medium, the BSFL prepupae could accumulate 58% of its biomass weight with lipid. The low polyunsaturated fatty acid (6%) and high C18:1 (50%) also guaranteed high biodiesel quality derived from BSFL. Nevertheless, the longer BSFL rearing duration when fed with week-6 self-fermented waste coconut endosperm had triggered a slight increase in protein yield (18%) in comparison with week-4 medium (15%). In considering of organic waste treatment advantage of week-4 self-fermented waste coconut endosperm, a total waste reduction of 0.019 g/d was successfully measured using only 20 BSFL. Therefore, week-4 self-fermented period was concluded as an optimum to produce ideal waste coconut endosperm feed medium for BSFL in enhancing the simultaneous lipid and protein yields

Assessing Microalgal Protein’s Impact on Environment and Energy Footprint via Life Cycle Analysis

Conventionally, increasing the yield of microalgal biomass has been the primary focus of research, while the significant protein reserve within this biomass has remained largely unexplored. This protein reserve possesses substantial value and versatility, offering a wide range of prospective applications and presenting an enticing chance for innovation and value enhancement for various sectors. Current study employed an innovative research approach that focused solely on the LCA of protein production potential from microalgal biomass, a lesser-explored aspects within this domain. Most environmental impact categories were shown to be significantly affected by cultivation phase because of the electrical obligation, followed by the harvesting and protein extraction phase. Still, the environmental aspect was seen to yield a minimal impact on global warming potential, i.e., 4 × 10–3 kg CO2, underscoring the ecologically favorable nature of the process. Conversely, the overall energy impact was seen to intensify with NEB of − 39.33 MJ and NER of 0.49, drawing attention to the importance of addressing the energy aspect to harness the full potential of microalgal protein production

Abreast insights of harnessing microalgal lipids for producing biodiesel: A review of improving and advancing the technical aspects of cultivation

In the pursuit of alternatives for conventional diesel, sourced from non-renewable fossil fuel, biodiesel has gained attentions for its intrinsic benefits. However, the commercial production process for biodiesel is still not sufficiently competitive. This review analyses microalgal lipid, one of the important sources of biodiesel, and its cultivation techniques with recent developments in the technical aspects. In fact, the microalgal lipids are the third generation feedstock, used for biodiesel production after its benefits outweigh that of edible vegetable oils (first generation) and non-edible oils (second generation). The critical factors influencing microalgal growth and its lipid production and accumulation are also discussed. Following that is the internal enhancement for cellular lipid production through genetic engineering. Moreover, the microalgae cultivation data modelling was also rationalized, with a specific focus on growth kinetic models that allow for the prediction and optimization of lipid production. Finally, the machine learning and environmental impact analysis are as well presented as important aspects to consider in fulfilling the prime objective of commercial sustainability to produce microalgal biodiesel

Assuaging microalgal harvesting woes via attached growth: A critical review to produce sustainable microalgal feedstock

Third-generation biofuels that are derived from microalgal biomass have gained momentum as a way forward in the sustainable production of biodiesel. Such efforts are propelled by the intention to reduce our dependence on fossil fuels as the primary source of energy. Accordingly, growing microalgal biomass in the form of suspended cultivation has been a conventional technique for the past few decades. To overcome the inevitable harvesting shortcomings arising from the excessive energy and time needed to separate the planktonic microalgal cells from water medium, researchers have started to explore attached microalgal cultivation systems. This cultivation mode permits the ease of harvesting mature microalgal biomass, circumventing the need to employ complex harvesting techniques to single out the cells, and is economically attractive. However, the main bottleneck associated with attached microalgal growth is low biomass production due to the difficulties the microalgal cells have in forming attachment and populating thereafter. In this regard, the current review encompasses the novel techniques adopted to promote attached microalgal growth. The physicochemical effects such as the pH of the culture medium, hydrophobicity, as well as the substratum surface properties and abiotic factors that can determine the fate of exponential growth of attached microalgal cells, are critically reviewed. This review aims to unveil the benefits of an attached microalgal cultivation system as a promising harvesting technique to produce sustainable biodiesel for lasting applications

Enhancing microalgal hydrogen production via photo-fermentative modelling with alimentation derived from palm kernel expeller

Microalgal hydrogen (H2) production via photo-fermentative process is an environmentally friendly alternative to the fossil fuel-based energy. Palm kernel expeller (PKE), a low-cost biomass had presented a significant advantage as organic nutrients' source in this study to fuel the photo-fermentative process. However, the increase of PKE concentrations beyond a threshold of 15.0 g/L had led to the decrease in H2 production. As this metabolic photo-fermentative process was driven by light illumination, it was essential to investigate the impact exerted by various light intensities on microalgal H2 productions. Accordingly, the oxygen (O2) concentration evolutions stemming from increasing photosynthetic dissolved oxygen (DO) concentrations within the culture mediums were evaluated and remodelled with the Andrew's substrate inhibition model. The absolute inhibition of photo-fermentation was predicted at 29.6 g/L of PKE with 0.006 g/L. day of photosynthetic oxygenation rate under a specific light intensity ranging from 100 to 500 μmol/m2s. On the other hand, at the optimum 5–15 g/L of PKE, the maximum H2 production rate could be attained at about 46 mL-H2/g-biomass.day with 200 μmol/m2s of light intensity. Further increasing of light intensities had also increased the photosynthetic activities, leading to the increased DO accumulations that favoured the culture photorespirations over photo-fermentative H2 productions. The sustainability of producing microalgal H2 was finally verified from the recycled study using a similar PKE organic nutrients' source to continuously generate H2 that had steadily maintained after the second cycle onwards with merely 4% of a gradual decrease until fourth cycle