• Energy Research

This case study examines the feasibility of the production of biochar from biosolids using energy neutral pyrolysis process using ASPEN Plus process modeling followed by a detailed techno‐economic assessment. The modeling exercise demonstrated that the pyrolysis can be energy neutral with moisture content in biosolids as high as 50 wt.%. In the case of moisture content lower than 50%, surplus energy will be available which can be converted to electrical energy; generating additional revenue. Further analysis on the effect of pyrolysis temperature on surplus energy available revealed that surplus energy increased when pyrolysis temperature reached from 450 to 650°C, but it gradually decreased above 650°C. The techno‐economics analysis suggested that biosolids management cost and biochar sale price were the most critical sensitivity factors while capital and operating costs of the pyrolysis unit seemed to be less critical. The positive Net Present Value values in scenario modeling suggest that the conversion of biosolids to biochar using energy neutral pyrolysis process looks promising and is techno‐economically feasible for most of the studied scenarios. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13113, 2019

Biofuel produced by fast pyrolysis from biomass is a promising candidate. The heart of the system is a reactor which is directly or indirectly heated to approximately 500°C by exhaust gases from a combustor that burns pyrolysis gas and some of the by-product char. In most of the cases, external biomass heater is used as heating source of the system while internal electrical heating is recently implemented as source of reactor heating. However, this heating system causes biomass or other conventional forms of fuel consumption to produce renewable energy and contributes to environmental pollution. In order to overcome these, the feasibility of incorporating solar energy with fast pyrolysis has been investigated. The main advantages of solar reactor heating include renewable source of energy, comparatively simpler devices, and no environmental pollution. A lab scale pyrolysis setup has been examined along with 1.2 m diameter parabolic reflector concentrator that provides hot exhaust gas up to 162°C. The study shows that about 32.4% carbon dioxide (CO2) emissions and almost one-third portion of fuel cost are reduced by incorporating solar heating system. Successful implementation of this proposed solar assisted pyrolysis would open a prospective window of renewable energy.

Abstract Slow pyrolysis of regenerated cellulose-rich material (RCRM) and recovered lignin produced from imidazolium-based ionic liquid (IL) pre-treatment of sugarcane straw (SCS) was investigated employing a Thermogravimetric Analyser (TGA) instrument coupled with a Fourier-Transform Infrared (FTIR) spectroscopy. 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) pre-treatment of SCS altered the hydrogen bonds of cellulose and produced amorphous Cellulose II structure in RCRM. FTIR spectroscopic analysis of liquid products showed that the IL pre-treatment increased the production of furans from the pyrolysis of RCRM, because the presence of amorphous Cellulose II in RCRM enhanced the dehydration reaction during pyrolysis. Moreover, the recovered lignin from IL pre-treatment enhanced the production of phenol-rich pyrolysis oil due to the cleavage of β-O-4 ether bonds of lignin during pre-treatment. Scanning electron microscope (SEM) analysis indicated highly porous structure of both RCRM and recovered lignin derived biochars. The kinetic analysis using a hybrid approach (a combination of model-fitting and model-free methods) indicated a reduction in the activation energy for both RCRM and recovered lignin pyrolysis. It is concluded that IL pre-treatment of lignocellulosic biomass followed by low-temperature pyrolysis can be an efficient route for biorefinery production.

Abstract Biogas technology is one of the prevalent alternative ways to mitigate energy crisis in Bangladesh. This approach of renewable energy is becoming popular to the rural population due to its economic viability and environmental attractiveness. The aim of this review paper is to illustrate the current status of domestic biogas plants in Bangladesh. The study also assesses the total biomass potential including livestock manure and agricultural residue available for biogas generation. The assessment shows that the total estimated amount of residues is 106.27 million tons comprises 42.49 million tons from agricultural residue, and 63.78 million tons from livestock manure and municipal solid waste (MSW) which is equivalent to 5.045 billion m3 of biogas. The economic analysis of 2.0 m3, 2.6 m3, and 3.2 m3 family size biogas plants are found to be a viable option in substitution of biomass and other commercial energy. The reliable supply of low-cost feed materials for biogas production has found to be an important factor to make the plant more feasible.

Abstract Bangladesh is energy starve country facing a severe power crisis for the last few decades because of inadequate power generation capacity compared with demand. The power generation of the country largely depends on the non-renewable (fossil fuel) energy sources, mainly on the natural gas as accounts 64.5% of recent installed capacity. This trend causes rapid depletion of non-renewable energy sources. Thus, it is necessary to trim down the dependency on non-renewable energy sources and utilize the available renewable resources to meet the huge energy demand facing the country. Most of the people living in rural, remote, coastal and isolated areas in Bangladesh have no electricity access yet. However, renewable energy resources, especially biomass can play a pivotal role to electrify those rural, remote, coastal and isolated areas in the country. Humankind has been using biomass as an energy source for thousands of years. This study assesses the bio-energy potential, utilization and related Renewable Energy Technologies (RETs) practice in Bangladesh. Improved cooking stove, biogas plant and biomass briquetting are the major RETs commonly practiced in Bangladesh. The assessment includes the potential of agricultural residue, forest residue, animal manure and municipal solid waste. The estimated total amount of biomass resource available for energy in Bangladesh in 2012–2013 is 90.21 million tons with the annual energy potential of 45.91 million tons of coal equivalent. The recoverable amount of biomass (90.21 million tons) in 2012–2013 has an energy potential of 1344.99 PJ which is equivalent to 373.71 TWh of electricity.

Biodiesel is an alternative, eco-friendly and renewable source of energy. It can be produced from a wide range of feedstocks which can be grown in marginal land use. It has drawn more attention to the researchers. In this study, the oil extraction, biodiesel conversion, and physiochemical properties of Macadamia (Macadamia integrifolia) and Grapeseed (Vitis vinifera) biodiesels are presented. The experimental investigation of diesel engine performance, emissions and combustion characteristics were conducted using B5 (5% biodiesel and 95% diesel by volume) and B10 (10% biodiesel and 90% diesel by volume) blends. The engine performance parameters, such as brake power (BP), brake specific fuel consumption (BSFC), and brake thermal efficiency (BTE) have been investigated in this experiment. The emission parameters, for example, carbon monoxide (CO), the ratio of CO2/CO, nitrogen oxide (NOx), hydrocarbon (HC), particulate matter (PM) have been measured during the experiment. Finally, the combustion parameters such as cylinder pressure (CP) were recorded, and heat release rate (HRR) was analysed and compared with that of diesel fuel. The study revealed that the Macadamia biodiesel performed better than Grapeseed biodiesel and behaved closely to that of diesel fuel. A significant reduction of engine emissions was found in the case of Macadamia biodiesel with a minimal reduction of engine performance. Further analysis of energy, exergy and tribological characteristics of the Macadamia biodiesel is recommended for assessing its feasibility for commercial application.

The need for liquid and gaseous fuel for transportation application is growing very fast. This high consumption trend causes swift exhaustion of fossil fuel reserve as well as severe environment pollution. Biogas can be converted into various renewable automobile fuels such as bio-CNG, syngas, gasoline, and liquefied biogas. However, bio-CNG, a compressed biogas with high methane content, can be a promising candidate as vehicle fuel in replacement of conventional fuel to resolve this problem. This paper presents an overview of available liquid and gaseous fuel commonly used as transportation fuel in Bangladesh. The paper also illustrates the potential of bio-CNG conversion from biogas in Bangladesh. It is estimated that, in the fiscal year 2012-2013, the country had about 7.6775 billion m3 biogas potential equivalent to 5.088 billion m3 of bio-CNG. Bio-CNG is competitive to the conventional automobile fuels in terms of its properties, economy, and emission.

There are several recent reviews published in the literature on hydrothermal carbonization, liquefaction and supercritical water gasification of lignocellulosic biomass and algae. The potential of hydrochar, bio-oil or synthesis gas production and applications have also been reviewed individually. The comprehensive review on the hydrothermal treatment of wet wastes (such as municipal solid waste, food waste, sewage sludge, algae) covering carbonization, liquefaction and supercritical water gasification, however, is missing in the literature which formed the basis of the current review paper. The current paper critically reviews the literature around the full spectrum of hydrothermal treatment for wet wastes and establishes a good comparison of the different hydrothermal treatment options for managing wet waste streams. Also, the role of catalysts as well as synthesis of catalysts using hydrothermal treatment of biomass has been critically reviewed. For the first time, efforts have also been made to summarize findings on modelling works as well as techno-economic assessments in the area of hydrothermal treatments of wet wastes. The study concludes with key findings, knowledge gaps and future recommendations to improve the productivity of hydrothermal treatment of wet wastes, helping improve the commercial viability and environmental sustainability.