Upgrading of Olive Tree Trimmings Residue as Biofuel by Hydrothermal Carbonization and Torrefaction: a Comparative Study (original) (raw)
International Journal of Engineering & Technology
Olive pomace is a by-product of olive oil production process and has the potential to be a solid biofuel after thermal treatment. In this study, olive pomace was treated by two thermal conversion methods: hydrothermal carbonization (HTC) and torrefaction. Experiments were carried out under the temperature values of 250, 275, 300 and 350°C; reaction times of 10, 20 and 30 minutes for torrefaction and temperature values of 180, 200 and 220°C; reaction time of 2, 3 and 4 hours for HTC. Products with the same energy yield value (62 %) obtained the higher heating values of 23.73 and 25.20 MJ/kg for torrefaction (275°C for 20 minutes) and hydrothermal carbonization (220°C for 2 hours), respectively. Hydrothermal carbonization method has the potential to produce chars at lower temperature values and without a drying process; and obtain products with improved higher heating values, energy yields and atomic O/C and H/C ratios compare to torrefaction products.
Olive‐derived biomass as a source of energy and chemicals
Biofuels, Bioproducts and Biorefining, 2017
Olive trees are cultivated in more than 40 countries worldwide over more than 10 million hectares. In addition to olive oil, a large amount of biomass is produced annually. All this biomass must be adequately handled and disposed of. Conventional disposal methods include direct burning or spreading in fi elds, but this has economical costs and environmental concerns, as well as wasting a source of energy and chemicals. This review summarizes the most recent proposals for the use of biomass derived from olive tree cultivation and olive oil production processes. Biomass produced from pruning, leaves, olive stones and pomace, extracted olive pomace, and olive waste water are considered, and the main options for processing are reviewed according to recent advances in the literature. The biorefi nery concept applied to olive-derived biomass is also presented and representative works are discussed.
Effects of Torrefaction on Carbonization Characteristics of Solid Olive Mill Residue
BioResources, 2016
Torrefaction is an important biomass pretreatment method that impacts fuel characteristics of biomass, specifically during the torrefaction process. Besides improving the fuel characteristics of biomass, torrefaction also contributes to increased quality of liquid and gaseous energy carriers obtained from fast pyrolysis and gasification. In this study, the effect of torrefaction on the solid energy carrier biochar, produced by carbonization, was studied by using solid olive mill residue (SOMR) as raw biomass. The carbonization characteristics of SOMR and torrefied SOMR (tSOMR) were compared by using ultimate and proximate analysis results. The higher heating value (HHV) and energy yields of biochars produced from SOMR and tSOMR were compared. The results showed that torrefaction contributed to the reduction of energy given to the biomass during the carbonization process by decreasing the holding time.
One stage olive mill waste streams valorisation via hydrothermal carbonisation
Waste Management, 2018
An olive waste stream mixture, coming from a three phase-continuous centrifugation olive oil mill industry, with a typical wet basis mass composition of olive pulp 39 wt%, kernels 5 wt% and olive mill waste water 56 wt%, was subjected to hydrothermal carbonisation (HTC) at 180, 220 and 250°C for a 3-hour residence time in a 2-litre stainless steel electrically heated batch reactor. The raw feedstock and corresponding hydrochars were characterised in terms of proximate and ultimate analyses, higher heating values and energy properties. Results showed an increase in carbonisation of samples with increasing HTC severity and an energy densification ratio up to 142% (at 250°C). Hydrochar obtained at 250°C was successfully pelletised using a lab scale pelletiser without binders or expensive drying procedures. Energy characterisation (HHV, TGA), ATR-FTIR analysis, fouling index evaluation and pelletisation results suggested that olive mill waste hydrochars could be used as energy dense and mechanical stable biofuels. Characterisation of HTC residues in terms of mineral content via induced coupled plasma optical emission spectroscopy (ICP-OES) as well as Total and Dissolved Organic Carbon enabled to evaluate their potential use as soil improvers. Nutrients and polyphenolic compounds in HTC liquid fractions were evaluated for the estimation of their potential use as liquid fertilisers. Results showed that HTC could represent a viable route for the valorisation of olive mill industry waste streams.
Processes, 2020
Hydrothermal carbonization (HTC) allows the conversion of organic waste into a solid product called hydrochar with improved fuel properties. Olive tree pruning biomass (OTP), a very abundant residue in Mediterranean countries, was treated by HTC to obtain a solid fuel similar to coal that could be used in co-combustion processes. Three different reaction temperatures (220, 250, and 280 °C) and reaction times (3, 6, and 9 h) were selected. The hydrochars obtained were extensively analyzed to study their behavior as fuel (i.e., ultimate, proximate, fiber and thermogravimetric analysis, Fourier-transform infrared spectroscopy (FTIR), activation energy, and combustion performance). The concentrations of cellulose, hemicellulose, and lignin in the samples depict a clear and consistent trend with the chemical reactions carried out in this treatment. Regarding O/C and H/C ratios and HHV, the hydrochars generated at more severe conditions are similar to lignite coal, reaching values of HHV ...
Torrefaction of Solid Olive Mill Residue
Bioresources, 2015
Solid olive mill residue (SOMR), a lignocellulosic material obtained from olive oil extraction, is a potential attractive source of biomass for energy generation. Although SOMR can be directly combusted, a pretreatment can reduce the oxygen and moisture contents of raw SOMR for efficient energy generation. Torrefaction is a promising thermal pretreatment method for improving fuel characteristics of raw SOMR. In this study, torrefaction characteristics of SOMR were investigated at three different torrefaction temperatures and holding times. Ultimate and proximate analysis results of torrefied SOMR were compared with dried SOMR. Results indicate that an increased torrefaction temperature and holding time can lead to a more qualified solid fuel with higher carbon content, increased higher heating value (HHV), and reduced oxygen content. Further, increased HHV and removal of volatiles are indicators of more energy-dense solid fuel obtained from SOMR. Experimental results revealed that moderately severe torrefaction conditions with holding times not exceeding 30 minutes are suitable for torrefaction of SOMR.
Biorefinery based on olive biomass. State of the art and future trends
Bioresource Technology, 2014
h i g h l i g h t s Olive trees cultivation has spread worldwide. Review outlines olive tree pruning biomass as feedstock in a biorefinery concept. Co-products and residues from cultivation and olive oil production were identified. Olive tree pruning revalorized by transforming into value-added products. An integrated biorefinery scheme based on olive tree pruning is proposed.
Determination of the Optimal Operative Conditions for the Torrefaction of Olive Waste Biomass
Sustainability, 2020
The need for new energy sources and the problems associated with waste in the agroforestry industry are an opportunity for the recovery of this waste. For the use of this agricultural waste as energy, different pretreatments, such as torrefaction, can be carried out. Torrefaction is a thermochemical treatment involving energetic densification of biomass at temperatures ranging from 200 to 300 °C under an inert and anaerobic environment. This study developed a numerical model to evaluate the effect of temperature and residence time of torrefaction on biomass from olive tree waste to determine optimum operative conditions for the process. Four temperatures and four residence times, in the operation range of the process, were tested to determine the weight loss and the higher heating values (HHVs) of the torrefied sample. From these data, a numerical model was developed to infer the complete behavior of the process in the temperature range between 200 and 300 °C and in the residence ti...
OLIVE RESIDUES TO ENERGY CHAINS IN THE APULIA REGION PART I: BIOMASS POTENTIALS AND COSTS
2009
Abstract The main objective of the proposed research is to estimate the energy potentials of the olive trees pruning residues and olive husk residues in the Apulia region (Southern Italy) and to compare the possible bioenergy conversion routes for heat and power generation. 46 006_Pantaleo (537) _37 27-07-2009 11: 20 Pagina 46 The part I of the research proposes a preliminary review of the olive oil chain residues in the Apulia region and an assessment of technical potentials and biomass supply costs.
Hydrothermal carbonization of dried olive pomace: Energy potential and process performances
Journal of Analytical and Applied Pyrolysis, 2017
Hydrothermal carbonization (HTC) of dried olive pomace (DOP) was performed in subcritical water under HTC conditions (180-250 °C) to assess the potential of the generated hydrochar to produce energy. The effects of process parameters (holding time, temperature and DOP/water weight ratio) on the yield and the quality of the hydrochar were examined. The mass yield of hydrochar was between 56% and 71% and its HHV increased by more than 23% compared to the HHV of DOP giving a hydrochar similar to a lignite type coal. The results reveal that a 30 min treatment at 215 °C with DOP/water weight ratio of 1/6 maximizes the energy yield (83%) of the HTC process. Both the DOP and the hydrochar were characterized by ultimate, proximate and thermogravimetric analyses. The ultimate and thermogravimetric analyses showed that the hydrochar is more carbonaceous and more thermally stable than untreated DOP. The HTC conversion of raw DOP was carried out by dehydration reactions. The proximate analysis showed that hydrochars contained lower ash and volatile matter compared to the raw DOP.