Organic Waste Torrefaction – A Review: Reactor Systems, and the Biochar Properties

Torrefaction is a thermochemical process in a narrow temperature ranging from 200 to 300°C, where primarily hemicellulose fibers are depolymerized. This process is carried out under atmospheric pressure and in anaerobic conditions; heating ratio is low (<50°C/min) and the residence time is relatively long, up to 1 h. During the process, a biomass is partially decomposed and forms different condensing and noncondensing gases. The final product is a constant substance rich in carbon, which is called a torrefied biomass—biochar and biocarbon. Currently an increase in energy demand is impacting the environment considerably. For this reason, in this chapter the organic waste torrefaction technology will be presented, including the reactor systems review. Torrefaction process may be conducted in different types of reactors, with diverse technologies. From this variety, two main groups of reactors can be distinguished, with direct and indirect heating. Direct heating group consists of reactors with multiple design, such as Multiple Hearth Furnace, microwave reactor, moving bed, vibrating belt, the reactor belt, and auger. Indirect heating reactors are less common and this group consists of rotating drum and auger reactor. All mentioned reactor types will be presented and discussed

Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars

We propose a ‘Waste to Carbon’ thermal transformation of sewage sludge (SS) via torrefaction to a valuable product (fuel) with a high content of carbon. One important, technological aspect to develop this concept is the determination of activation energy needed for torrefaction. Thus, this research aimed to evaluate the kinetics of SS torrefaction and determine the effects of process temperature on fuel properties of torrefied products (biochars). Torrefaction was performed using high ash content SS at six (200~300 °C) temperatures and 60 min residence (process) time. Mass loss during torrefaction ranged from 10~20%. The resulting activation energy for SS torrefaction was ~12.007 kJ·mol−1. Initial (unprocessed) SS higher heating value (HHV) was 13.5 MJ·kg−1. However, the increase of torrefaction temperature decreased HHV from 13.4 to 3.8 MJ·kg−1. Elemental analysis showed a significant decrease of the H/C ratio that occurred during torrefaction, while the O/C ratio fluctuated with much smaller differences. Although the activation energy was significantly lower compared with lignocellulosic materials, low-temperature SS torrefaction technology could be explored for further SS stabilization and utilization (e.g., dewatering and hygienization)

High live birth rate after conservative treatment of ectopic pregnancy with Methotrexate

Objectives: The aim of the study was to assess fertility in patients diagnosed with ectopic pregnancy and treated with methotrexate, as well as safety and efficacy of conservative treatment. Also, risk factors of recurrent ectopic pregnancies were determined. Material and methods: The study included 86 female patients with ectopic pregnancy, hospitalized and treated in the clinic of Gynecological Endocrinology, UJCM, Cracow, between 2007 and 2011. A total of 73 patients received a single dose of MTX in the amount of 50mg/m2 of body surface area. Serum b-hCG concentration was measured on days 4 and 7. The treatment was considered successful when b-hCG concentrations dropped to less than 0.2mIU/ml without surgery. Results: Among 34 patients on follow-up, 8 (23.5%) did not attempt to conceive again, whereas 26 patients declared their wish to conceive again. The attempt proved to be successful in case of 16 women (61.53%), and they gave birth to healthy children. Average time to pregnancy was 14.9 months (S

Food Waste Management Using the Hermetia Illucens Insect

In modern agricultural biogas plants, the biowastes are being increasingly used for the biogas production. The food waste is also widely used in larvae breeding. This is an important because, based on biowaste, its proper management and green energy production is possible. This study aims to determine the biogas and methane efficiency of the Hermetia illucens larvae that were fed using the food waste. In the research on the biogas and methane efficiency, the Hermetia illucens larvae were used. The total solids (TS) of the substrate equals 30.35%, and the volatile solids (VS) content was 92.31% of TS. The larvae were fed only with the food waste of plant origin. The obtained substrates were homogeneous. The experiment was carried out under mesophilic anaerobic digestion conditions – 39°C in the 21-chamber biofermentor set in the Institute of Biosystems Engineering in Poznań University of Life Sciences. The anaerobic digestion process in the batch reactor ran correctly. Fermentation inhibition was not detected. The biogas efficiency for larvae amounted to 198.75 m3∙Mg-1 fresh mass (FM). On the other hand,the methane efficiency, amounted to 127.73 m3∙Mg-1, at the methane concentration of 64.27%. On the basis of the research, it was found that the larvae feeding on food waste can be used directly as anaerobic digestion in the bioconversion process

Is the biochar produced from sewage sludge a good quality solid fuel?

The influence of sewage sludge torrefaction temperature on fuel properties was investigated. Non-lignocellulosic waste thermal treatment experiment was conducted within 1 h residence time, under the following temperatures: 200, 220, 240, 260, 280 and 300°C. Sawdust was used as lignocellulosic reference material. The following parameters of biochar have been measured: moisture, higher heating value, ash content, volatile compounds and sulfur content. Sawdust biochar has been confirmed to be a good quality solid fuel. High ash and sulfur content may be an obstacle for biochar energy reuse. The best temperature profile for sawdust torrefaction and fuel production for 1 h residence time was 220°C. At this temperature the product contained 84% of initial energy while decreased the mass by 25%. The best temperature profile for sewage sludge was 240°C. The energy residue was 91% and the mass residue was 85%. Higher temperatures in both cases caused excessive mass and energy losses

The potential of agricultural biogas against other types of renewable energy sources

Przedstawiono potencjał biogazu rolniczego bazującego na wykorzystaniu bioodpadów i roślin specjalnie przeznaczonych dla biogazowni. Określono zalety energetyki biogazowej jako w pełni kontrolowalnej oraz zestawiono je z problemami stwarzanymi przez energetykę niestabilną w kraju i zagranicą. Przedstawiono także kierunki rozwoju sektora biogazu rolniczego w Polsce.The paper presents the potential of agricultural biogas based both on the use of bio-waste and plants dedicated to biogas plants. The advantages of biogas power engineering were determined as fully controllable and compared with problems generated by unstable energy. The directions of development of the agricultural biogas sector in Poland were also presented

Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars

We propose a ‘Waste to Carbon’ thermal transformation of sewage sludge (SS) via torrefaction to a valuable product (fuel) with a high content of carbon. One important, technological aspect to develop this concept is the determination of activation energy needed for torrefaction. Thus, this research aimed to evaluate the kinetics of SS torrefaction and determine the effects of process temperature on fuel properties of torrefied products (biochars). Torrefaction was performed using high ash content SS at six (200~300 °C) temperatures and 60 min residence (process) time. Mass loss during torrefaction ranged from 10~20%. The resulting activation energy for SS torrefaction was ~12.007 kJ·mol−1. Initial (unprocessed) SS higher heating value (HHV) was 13.5 MJ·kg−1. However, the increase of torrefaction temperature decreased HHV from 13.4 to 3.8 MJ·kg−1. Elemental analysis showed a significant decrease of the H/C ratio that occurred during torrefaction, while the O/C ratio fluctuated with much smaller differences. Although the activation energy was significantly lower compared with lignocellulosic materials, low-temperature SS torrefaction technology could be explored for further SS stabilization and utilization (e.g., dewatering and hygienization).This article is published as Pulka, Jakub; Manczarski, Piotr; Koziel, Jacek A.; Białowiec, Andrzej. "Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars." Energies 12, no. 3 (2019): 565. DOI: 10.3390/en12030565. Posted with permission.</p

Reduction of Greenhouse Gas Emissions by Replacing Fertilizers with Digestate

Digestate from a biogas plant can be a valuable organic and mineral fertilizer. Quantitative proportions of cosubstrates used in three agricultural biogas plants in Poland were analyzed. The composition of digestates was examined and large differences in the content of macronutrients were found, especially N and K. On the basis of the factors used to calculate emissions from the production and use of artificial fertilizers, the greenhouse gas (GHG) reduction resulting from replacing mineral fertilizers with digestate was calculated. In terms of 1 Mg of fresh digestate, this reduction may not seem large, as it amounts to 27.9–61.6 kg of CO2 eq, but it should be taken into account that digestate contains little dry matter. The annual amount of digestate used on an area of 1 ha allows avoiding GHG emissions of 25.8–44.5 Mg CO2 eq

Waste as substrates for agricultural biogas plants : A case study from Poland

Energy production from renewable sources is one of the main ways to fight against global warming. Anaerobic digestion process can be used to produce biogas containing methane. In the light of the growing demand for substrates, a variety of raw materials are required. These substrates should be suitable for anaerobic digestion, and processing them need to provide the desired amount of energy. This paper aims to discuss the agricultural biogas market in Poland, its current state, and the possibility of development during energy transformation, in particular in terms of using waste as a substrate for energy production. In February 2022, there were 130 agricultural biogas plants registered in Poland. On the other hand, in 2020, 4,409,054.898 Mg of raw materials were used to produce agricultural biogas in Poland. Among all the substrates used, waste played a special role. With the right amount of raw materials and proper management of a biogas plant, it is possible to produce electricity and provide stable and predictable heat supply. Bearing in mind the development of the Polish and European biogas markets, attention should be paid to ensure access to raw materials from which chemical energy in the form of biogas can be generated. Due to limited access to farmland and the increasing demand for food production, one should expect that waste will be increasingly often used for biogas production, especially that with high energy potential, such as waste related to animal production and the meat industry

Waste-to-Carbon: Is the Torrefied Sewage Sludge with High Ash Content a Better Fuel or Fertilizer?

Sewage sludge (SS) recycling is an important part of the proposed &lsquo;circular economy&rsquo; concept. SS can be valorized via torrefaction (also known as &lsquo;low-temperature pyrolysis&rsquo; or &lsquo;roasting&rsquo;). SS can, therefore, be considered a low-quality fuel or a source of nutrients essential for plant growth. Biochar produced by torrefaction of SS is a form of carbonized fuel or fertilizer. In this research, for the first time, we tested the feasibility of torrefaction of SS with high ash content for either fuel or organic fertilizer production. The research was conducted in 18 variants (six torrefaction temperatures between 200~300 &deg;C, and three process residence times of 20, 40, 60 min) in 5 repetitions. Fuel and fertilizer properties and multiple regression analysis of produced biochar were conducted. The higher heating value (HHV) of raw SS was 21.2 MJ&middot;kg&minus;1. Produced biochar was characterized by HHV up to 12.85 MJ&middot;kg&minus;1 and lower H/C and O/C molar ratio. Therefore, torrefaction of SS with high ash content should not be considered as a method for improving the fuel properties. Instead, the production of fertilizer appears to be favorable. The torrefaction increased C, N, Mg, Ca, K, Na concentration in relation to raw SS. No significant (p &lt; 0.05) influence of the increase of temperature and residence time on the increase of biogenic elements in biochar was found, however the highest biogenic element content, were found in biochar produced for 60 min, under the temperature ranging from 200 to 240 &deg;C. Obtained biochars met the Polish regulatory criteria for mineral-organic fertilizer. Therefore SS torrefaction may be considered a feasible waste recycling technology. The calculation of torrefaction energy and the mass balance shows energy demand &lt;2.5 GJ∙Mg&minus;1 w.m., and the expected mass yield of the product, organic fertilizer, is ~178 kg∙Mg&minus;1 w.m of SS. Further investigation should consider the scaling-up of the SS torrefaction process, with the application of other types of SSs