Ganesh K. Parshetti

Chemical, structural and combustion characteristics of carbonaceous products obtained by hydrothermal carbonization of palm empty fruit bunches.

A carbon-rich solid product, denoted as hydrochar, was synthesized by hydrothermal carbonization (HTC) of palm oil empty fruit bunch (EFB), at different pre-treatment temperatures of 150, 250 and 350 °C. The conversion of the raw biomass to its hydrochar occurred via dehydration and decarboxylation processes. The hydrochar produced at 350 °C had the maximum energy-density (>27 MJ kg(-1)) with 68.52% of raw EFB energy retained in the char. To gain a detailed insight into the chemical and structural properties, carbonaceous hydrochar materials were characterized by FE-SEM, FT-IR, XRD and Brunauer-Emmett-Teller (BET) analyses. This work also investigated the influence of hydrothermally treated hydrochars on the co-combustion characteristics of low rank Indonesian coal. Conventional thermal gravimetric analysis (TGA) parameters, kinetics and activation energy of different hydrochar and coal blends were estimated. Our results show that solid hydrochars improve the combustion of low rank coals for energy generation.

Food waste-to-energy conversion technologies: current status and future directions.

Food waste represents a significantly fraction of municipal solid waste. Proper management and recycling of huge volumes of food waste are required to reduce its environmental burdens and to minimize risks to human health. Food waste is indeed an untapped resource with great potential for energy production. Utilization of food waste for energy conversion currently represents a challenge due to various reasons. These include its inherent heterogeneously variable compositions, high moisture contents and low calorific value, which constitute an impediment for the development of robust, large scale, and efficient industrial processes. Although a considerable amount of research has been carried out on the conversion of food waste to renewable energy, there is a lack of comprehensive and systematic reviews of the published literature. The present review synthesizes the current knowledge available in the use of technologies for food-waste-to-energy conversion involving biological (e.g. anaerobic digestion and fermentation), thermal and thermochemical technologies (e.g. incineration, pyrolysis, gasification and hydrothermal oxidation). The competitive advantages of these technologies as well as the challenges associated with them are discussed. In addition, the future directions for more effective utilization of food waste for renewable energy generation are suggested from an interdisciplinary perspective.

Hydrothermal conversion of urban food waste to chars for removal of textile dyes from contaminated waters

Hydrothermal carbonization of urban food waste was carried out to prepare hydrochars for removal of Acridine Orange and Rhodamine 6G dyes from contaminated water. The chemical composition and microstructure properties of the synthesized hydrochars were investigated in details. Batch adsorption experiments revealed that hydrochars with lower degree of carbonization were more efficient in adsorption of dyes. Operational parameters such as pH and temperature had a strong influence on the dye uptake process. The adsorption equilibrium data showed excellent fit to the Langmuir isotherm. The pseudo-second-order kinetic model provided a better correlation for the experimental kinetic data in comparison to the pseudo-first-order kinetic model. Thermodynamic investigations suggested that dye adsorption onto hydrochars was spontaneous and endothermic. The mechanism of dye removal appears to be associated with physisorption. An artificial neural network (ANN)-based modelling was further carried out to predict the dye adsorption capacity of the hydrochars.

Enzyme-assisted hydrothermal treatment of food waste for co-production of hydrochar and bio-oil.

Food waste was subjected to enzymatic hydrolysis prior to hydrothermal treatment to produce hydrochars and bio-oil. Pre-treatment of food waste with an enzyme ratio of 1:2:1 (carbohydrase:protease:lipase) proved to be effective in converting food waste to the two products with improved yields. The carbon contents and calorific values ranged from 43.7% to 65.4% and 17.4 to 26.9 MJ/kg for the hydrochars obtained with the enzyme-assisted pre-treatment, respectively while they varied from 38.2% to 53.5% and 15.0 to 21.7 MJ/kg, respectively for the hydrochars obtained with no pre-treatment. Moreover, the formation of carbonaceous microspheres with low concentrations of inorganic elements and diverse surface functional groups was observed in the case of enzyme-assisted food waste hydrochars. The enzymatic pre-treatment also facilitated the formation of the bio-oil with a narrow distribution of organic compounds and with the highest yield obtained at 350 °C.

Plant derived porous graphene nanosheets for efficient CO2 capture

There is an urgent need for the mitigation of climate change through CO2 reduction technologies. In this work, we demonstrate a novel method for production of porous graphene-like nanosheets (PGLNS) from the lignocellulosic fiber of oil palm empty fruit bunches (EFB) by a thermal graphitization technique for efficient CO2 capture. We used a wide range of microscopic and spectroscopic techniques to provide insights into the morphological and structural characteristics of the synthesized PGLNS (with d-spacing of ∼0.35 nm and pore size of <1 nm) obtained from the EFB biomass. The PGLNS show excellent performance as adsorbents for post-combustion CO2 capture. At 25 °C and 1 bar pressure, the maximum CO2 uptake was 2.43 mmol g−1 which is considerably higher than other competitive CO2 adsorbents, including zeolite, activated carbon and some metal organic frameworks. The selectivity of the PGLNS for CO2 over N2 (SCO2/N2 = 18.7), computed from single component isotherms at conditions pertinent to post-combustion applications, is also much higher than that of most of the previously reported adsorbents. Moreover, the significantly low isosteric heat of adsorption (∼21 kJ mol−1) revealed the possibility of desorbing CO2 and regenerating the PGLNS for their repeated use at a much lower energy penalty.