Bioenergy and biorefinery

This paper aims to examine the potential of waste biorefineries in developing countries as a solution to current waste disposal problems and as facilities to produce fuels, power, heat, and value-added products. The waste in developing countries represents a significant source of biomass, recycled materials, chemicals, energy, and revenue if wisely managed and used as a potential feedstock in various biorefinery technologies such as fermentation, anaerobic digestion (AD), pyrolysis, incineration, and gasification. However, the selection or integration of biorefinery technologies in any developing country should be based on its waste characterization. Waste biorefineries if developed in developing countries could provide energy generation, land savings, new businesses and consequent job creation, savings of landfills costs, GHG emissions reduction, and savings of natural resources of land, soil, and groundwater. The challenges in route to successful implementation of biorefinery concept in the developing countries are also presented using life cycle assessment (LCA) studies.

Addressing the contemporary waste management is seeing a shift towards energy production while managing waste sustainably. Consequently, waste treatment through gasification is slowly taking over the waste incineration with multiple benefits, including simultaneous waste management and energy production while reducing landfill volumes and displacing conventional fossil fuels. Only in the UK, there are around 14 commercial plants built to operate on gasification technology. These include fixed bed and fluidized bed gasification reactors. Ultra-clean tar free gasification of waste is now the best available technique and has experienced a significant shift from two-stage gasification and combustion towards a one-stage system for gasification and syngas cleaning. Nowadays in gasification sector, more companies are developing commercial plants with tar cracking and syngas cleaning. Moreover, gasification can be a practical scheme when applying ultra-clean syngas for a gas turbine with heat recovery by steam cycle for district heating and cooling (DHC) systems. This chapter aims to examine the recent trends in gasification-based waste-to-energy technologies. Furthermore, types of gasification technologies, their challenges and future perspectives in various applications are highlighted in detail.

Biogas potential was explored for animal manure, wheat straw, food waste and rice straw. Batch experiments were performed at a laboratory scale using potential biomethane assays (BMP) for a period of 50 days. The biogas yield was observed higher when using rice straw (0.40 m3/kg VSadded) as a substrate, as compared to wheat straw (0.33 m3/kg VSadded) and animal manure (0.30 m3/kg VSadded) substrates. Around 10% of biogas was produced in the initial phase of 4 days for manure, wheat straw, and rice straw feedstocks. During the middle phase of 30 days for these feedstocks, 65 – 80% of biogas was produced. Less than 20% of biogas was produced during the final phase of last 16 days of the experiment. The biogas production from food waste was found lowest (0.02 m3/kg VSadded) among all substrates. Therefore, the anaerobic digestion (AD) of both food waste and animal manure is more suited in co-digestion fashion than mono-digestion.

District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. Abstract Pulp mills without black liquor recovery cycle could play a major role in employing black liquor gasification (BLG) to produce transport fuels. In conventional chemical pulp mills, black liquor is burnt in recovery boilers to generate steam and electricity to meet energy demands. The inorganic chemicals are reused for the digestion process. However, the energy content and inorganic chemicals are not recovered in small scale pulp mills especially in the developing countries which do not employ recovery cycle. This study investigates the potential of synthetic natural gas (SNG) production by integrating BLG island with a reference pulp mill without chemical recovery cycle. The improvements in overall energy efficiency are evaluated using performance indicators such as biofuel production potential, integrated system's efficiency, and energy ratios. The oxygen-blown circulating fluidized bed (CFB) gasification with direct causticization is integrated with reference pulp mill. The results showed considerable SNG production without external biomass import. However to compensate total electricity deficit, the electricity will be imported from the grid. There is a substantial CO 2 abatement potential of combining CO 2 capture using seloxol absorption, and CO 2 mitigation from SNG by replacing gasoline.

Bio-electrochemical degradation of pentachlorophenol was carried out in single as well as dual chambered microbial fuel cell (MFC) with simultaneous production of electricity. The maximum cell potential was recorded to be 787 and 1021 mV in single and dual chambered systems respectively. The results presented nearly 66 and 89% COD removal in single and dual chambered systems with corresponding power densities of 872.7 and 1468.85 mW m À2 respectively. The highest coulombic efficiency for single and dual chambered counterparts was found to be 33.9% and 58.55%. GC-MS data revealed that pentachlorophenol was more effectively degraded under aerobic conditions in dual-chambered MFC. Real-time polymerase chain reaction showed the dominance of exoelectrogenic Geobacter in the two reactor systems with a slightly higher concentration in the dual-chambered system. The findings of this work suggested that the aerobic treatment of pentachlorophenol in cathodic compartment of dual chambered MFC is better than its anaerobic treatment in single chambered MFC in terms of chemical oxygen demand (COD) removal and output power density.

District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. Abstract The fossil fuels accomplish almost 80% of the world energy needs. The ever increasing exploitation of fossil fuels has led to environmental pollution, global climate change and health problems to living beings. Hence to meet the needs of the future energy and to mitigate the environmental pollution, it is critical to look for the alternate fuels. Global energy infrastructure in the future is believed to be accomplished by the energy generated from the low-cost renewable resources. Algae biomass has emerged as a promising biofuel source, as microalgae-based biofuels are biodegradable, renewable, and eco-friendly in comparison to fossil driven fuels. This study aims to examine the importance of microalgae as an alternative renewable energy source and evaluate the key challenges in the production of microalgae biofuel.

Effects of media compositions on biomass and lipid accumulation of the isolate Chlorella sp. TISTR 8990 were investigated under a Plackett-Burman experimental design with mixotrophic cultivation conditions. Under this experimental design there were 15 different runs with ten factors-yeast extract, KH2PO4, MgSO4, FeSO4, MnCl2, CuSO4, Na2MoO4, H3BO3, ZnSO4 and pH. Cultures were grown mixotrophically under 16 h light and 8 h dark regime at 30 ºC for a period of 7 days. During the light regime, the light intensity at the surface of the vessels and agitation speed were set to 67.5 μmol photons m-2s-1 and 150 rpm, respectively. Initial cell concentration was set to an absorbance (A540) of 0.5. For high biomass production (2.2 g/L, run no. 6), the most effective and significant factors were yeast extract, KH2PO4, FeSO4 and ZnSO4 at concentrations 0.3 g/L, 0.3 g/L, 3 mg/L and 0.3 mg/L, respectively. Whereas for high lipid accumulation (19.59 %DCW, run no. 2), these were KH2PO4, pH and yeast extract, at a level of 1.7 g/L, 6.0 and 0.1 g/L, respectively. No significant factors were obtained for higher lipid content. The best treatment for biomass and lipid content was run no. 6, whose medium formula consisted of 0.3 g/L yeast extract, 1.7 g/L KH2PO4, 1.7 g/L MgSO4, 1 mg/L FeSO4, 0.9 mg/L MnCl2, and pH 7.0, together with fixed concentrations of glucose, NaHCO3 and KNO3 at 5 g/L, 0.05 g/L and 0.5 g/L, respectively.
Keywords: Biomass, Chlorella sp., mixotroph, Plackett-Burman design, single cell oils