Pilot-scale conversion of lime-treated wheat straw into bioethanol: quality assessment of bioethanol and valorization of side streams by anaerobic digestion and combustion

The limited availability of fossil fuel sources, worldwide rising energy demands and anticipated climate changes attributed to an increase of greenhouse gasses are important driving forces for finding alternative energy sources. One approach to meeting the increasing energy demands and reduction of greenhouse gas emissions is by large-scale substitution of petrochemically derived transport fuels by the use of carbon dioxide-neutral biofuels, such as ethanol derived from lignocellulosic material. Results This paper describes an integrated pilot-scale process where lime-treated wheat straw with a high dry-matter content (around 35% by weight) is converted to ethanol via simultaneous saccharification and fermentation by commercial hydrolytic enzymes and bakers' yeast (Saccharomyces cerevisiae). After 53 hours of incubation, an ethanol concentration of 21.4 g/liter was detected, corresponding to a 48% glucan-to-ethanol conversion of the theoretical maximum. The xylan fraction remained mostly in the soluble oligomeric form (52%) in the fermentation broth, probably due to the inability of this yeast to convert pentoses. A preliminary assessment of the distilled ethanol quality showed that it meets transportation ethanol fuel specifications. The distillation residue, which contained non-hydrolysable and non-fermentable (in)organic compounds, was divided into a liquid and solid fraction. The liquid fraction served as substrate for the production of biogas (methane), whereas the solid fraction functioned as fuel for thermal conversion (combustion), yielding thermal energy, which can be used for heat and power generation. Conclusion Based on the achieved experimental values, 16.7 kg of pretreated wheat straw could be converted to 1.7 kg of ethanol, 1.1 kg of methane, 4.1 kg of carbon dioxide, around 3.4 kg of compost and 6.6 kg of lignin-rich residue. The higher heating value of the lignin-rich residue was 13.4 MJ thermal energy per kilogram (dry basis)

STRIDER (Sildenafil TheRapy in dismal prognosis early onset fetal growth restriction): An international consortium of randomised placebo-controlled trials

Background: Severe, early-onset fetal growth restriction due to placental insufficiency is associated with a high risk of perinatal mortality and morbidity with long-lasting sequelae. Placental insufficiency is the result of abnormal formation and function of the placenta with inadequate remodelling of the maternal spiral arteries. There is currently no effective therapy available. Some evidence suggests sildenafil citrate may improve uteroplacental blood flow, fetal growth, and meaningful infant outcomes. The objective of the Sildenafil TheRapy In Dismal prognosis Early onset fetal growth Restriction (STRIDER) collaboration is to evaluate the effectiveness of sildenafil versus placebo in achieving healthy perinatal survival through the conduct of randomised clinical trials and systematic review including individual patient data meta-analysis.  Methods: Five national/bi-national multicentre randomised placebo-controlled trials have been launched. Women with a singleton pregnancy between 18 and 30 weeks with severe fetal growth restriction of likely placental origin, and where the likelihood of perinatal death/severe morbidity is estimated to be significant are included. Participants will receive either sildenafil 25 mg or matching placebo tablets orally three times daily from recruitment to 32 weeks gestation.  Discussion: The STRIDER trials were conceived and designed through international collaboration. Although the individual trials have different primary outcomes for reasons of sample size and feasibility, all trials will collect a standard set of outcomes including survival without severe neonatal morbidity at time of hospital discharge. This is a summary of all the STRIDER trial protocols and provides an example of a prospectively planned international clinical research collaboration. All five individual trials will contribute to a pre-planned systematic review of the topic including individual patient data meta-analysis

Technical and environmental performance of lower carbon footprint cement mortars containing biomass fly ash as a secondary cementitious material

This study evaluated the mechanical and environmental properties of cement mortars containing fly ash from biomass combustion as a secondary cementitious material. Cement mortars with 20 and 40% wt. replacement of Portland cement with fly ash from two types of installations were tested for their compressive strength and leaching behaviour. Substitution of 20% Portland cement with wood fly ash complied with the reference standard for compressive strength of 42.5öMPa at 28ödays. Replacement rates of 40% developed a lower strength (30 and 33.5öMPa), but were still suitable for applications. The pulverized fuel ash perform substantially worse. We conclude that the biomass fly ash from fluidized bed combustion performs as a functional secondary cementitious material in cement, whereas the functionality of pulverized fuel fly ash is insufficient. The release of environmentally relevant elements from all the tested specimens fulfilled the Dutch leaching criteria for reuse. During second life as a granular construction material the release of Ba, Cr, Mo and V increased to a level of concern. However, this release was found to be similar to that of existing blended cements and was controlled by cement chemistry. The technical performance of cement mortars was influenced by the type and ratio of fly ash mixed with cement. However, the environmental performance was driven by the cement matrix that controlled the release of contaminants. Using biomass fly ash as a secondary cementitious material can reduce the carbon footprint of concrete by 40% while maintaining good technical and environmental performance

Evaluating Biomass Ash Properties as Influenced by Feedstock and Thermal Conversion Technology towards Cement Clinker Production with a Lower Carbon Footprint

Purpose: This study evaluates the potential of biomass ash as raw clinker material and the influence of biomass feedstock and thermal conversion technology on biomass ash properties. Methods: A set of criteria for biomass feedstock and ash properties (i.e. CaO/SiO2 ratio and burnability) are established. A large dataset was collected and the best combination of biomass feedstock and conversion technology regarding the desired ash quality was identified. Results: Wood biomass has the highest potential to provide the right CaO/SiO2 ratio which is needed to form clinker minerals. Bark content and exogenous Si inclusion in wood biomass have a large influence on the CaO/SiO2 ratio. Paper sludge is composed of Ca, Si and Al and can potentially serve as a source of cement elements. Wood fly ash from pulverized fuel combustion can substitute a considerable amount of raw clinker materials due to its similar burnability. The replacement ratio is determined by the content of adverse elements in the ash (i.e. MgO2 and P2O5). Conclusion: Using biomass ash to lower the CO2 emission from clinker production depends on the joint effort of bioenergy producers, by providing higher quality biomass ash, and cement makers, by adapting the kiln operation to enable a high level of raw material replacement by biomass ash.The presented evaluation of the ash production chain, from biomass selection through combustion technology and ash management, provides new insights and recommendations for both stakeholders to facilitate this sustainable development. Graphic Abstract: [Figure not available: see fulltext.].</p

Technical and environmental performance of lower carbon footprint cement mortars containing biomass fly ash as a secondary cementitious material

This study evaluated the mechanical and environmental properties of cement mortars containing fly ash from biomass combustion as a secondary cementitious material. Cement mortars with 20 and 40% wt. replacement of Portland cement with fly ash from two types of installations were tested for their compressive strength and leaching behaviour. Substitution of 20% Portland cement with wood fly ash complied with the reference standard for compressive strength of 42.5öMPa at 28ödays. Replacement rates of 40% developed a lower strength (30 and 33.5öMPa), but were still suitable for applications. The pulverized fuel ash perform substantially worse. We conclude that the biomass fly ash from fluidized bed combustion performs as a functional secondary cementitious material in cement, whereas the functionality of pulverized fuel fly ash is insufficient. The release of environmentally relevant elements from all the tested specimens fulfilled the Dutch leaching criteria for reuse. During second life as a granular construction material the release of Ba, Cr, Mo and V increased to a level of concern. However, this release was found to be similar to that of existing blended cements and was controlled by cement chemistry. The technical performance of cement mortars was influenced by the type and ratio of fly ash mixed with cement. However, the environmental performance was driven by the cement matrix that controlled the release of contaminants. Using biomass fly ash as a secondary cementitious material can reduce the carbon footprint of concrete by 40% while maintaining good technical and environmental performance

Life cycle assessment of the reuse of fly ash from biomass combustion as secondary cementitious material in cement products

In this study, we performed a life cycle assessment of the reuse of biomass fly ash as secondary cementitious material in cement mortars as alternative to a reference landfill scenario of the ash. Since biomass ash does contain enhanced levels of elements that are of potential concern for the environment or human exposure, the performed Life Cycle Assessment (LCA), in addition to CO2 savings, takes into account the impact on all non-toxic categories and human toxicity/carcinogenicity during service and second life stages. Results showed that utilization of biomass ash in cement is preferable over landfill for all the non-toxic categories at both cement replacements rates of 20 and 40 wt%. In detail, the reduction of CO2-eq. was found to be between 11 and 26% when biomass ash was blended with cement instead of being landfilled. The hydraulic activity of biomass ashes was found to be a critical parameter in this scenario, as it had impacts on the global warming potential (and all other investigated non-toxic categories), and it is therefore crucial to consider the uncertainty related to this aspect in LCA studies. Cement containing biomass ash performed better, on average, when compared with the reference landfill scenario regarding the impact to human toxicity (carcinogenic) category. Contrary, only the utilization in cement for one particular ash type (from paper sludge combustion) showed a better performance than the reference scenario for the ecotoxicity (ET) category. The impact to human toxicity carcinogenic (HTc) and ecotoxicity (ET) was mainly dominated by the leaching of Cr from landfilling of pure biomass fly ash (reference scenario) and the leaching of Ba, Cu, Cr (VI) and Zn from the second life stage of cement products (i.e., reuse of the crushed cement after service life in road base applications). However, this impact was acceptable when emissions are compared to existing EU landfill directive and regulations on the reuse of secondary materials in construction works. The novel LCA approach performed in this study, which includes impacts of leached contaminants during both the service and second life phase of cement, has shown that the reuse of biomass ash as secondary cementitious materials has a beneficial effect on the majority of the impact categories, with no unacceptable leaching risks.</p

Assessment of biomass ash applications in soil and cement mortars

The pH-dependent availability and leaching of major and trace elements was investigated for a wide range of biomass ash from different fuels and conversion technologies. A technical and environmental assessment of selected biomass ash for application in soil or cement mortars was performed, using both the total content and leaching of elements. A large variation in biomass ash composition, yet consistent pH dependent leaching patterns were observed for most elements and conversion technologies. Chromium showed a distinct behaviour which was hypothesized to reflect redox conditions during conversion of the biomass. The leaching based approach was found to provide a more realistic assessment of the availability of desired (i.e. nutrients) and undesired elements (i.e. contaminants) in soil systems. When applied to a reference soil at a rate of 2% by weight, the selected biomass ash increased the concentration of particularly Cr, Mo and Zn in soil solution to a level of concern. For cement applications, the release of Ba, Cr and Mo can become of concern during the second life stage, but the release was not attributed to the included biomass ash. Both soil and cement matrixes were found to control the release of elements such as Cu, V and Ni (soil) and As, Cr and Mo (cement) when compared to the released from pure biomass ash, underlining the importance of evaluating the availability and leaching of desired and undesired elements in the application scenario. Given current regulatory criteria, beneficial utilization of biomass ash in cement may be more feasible than in soil, but regulatory criteria based on leaching rather than total content of elements may widen the application potential of biomass ash

Life cycle assessment of the reuse of fly ash from biomass combustion as secondary cementitious material in cement products

In this study, we performed a life cycle assessment of the reuse of biomass fly ash as secondary cementitious material in cement mortars as alternative to a reference landfill scenario of the ash. Since biomass ash does contain enhanced levels of elements that are of potential concern for the environment or human exposure, the performed Life Cycle Assessment (LCA), in addition to CO2 savings, takes into account the impact on all non-toxic categories and human toxicity/carcinogenicity during service and second life stages. Results showed that utilization of biomass ash in cement is preferable over landfill for all the non-toxic categories at both cement replacements rates of 20 and 40 wt%. In detail, the reduction of CO2-eq. was found to be between 11 and 26% when biomass ash was blended with cement instead of being landfilled. The hydraulic activity of biomass ashes was found to be a critical parameter in this scenario, as it had impacts on the global warming potential (and all other investigated non-toxic categories), and it is therefore crucial to consider the uncertainty related to this aspect in LCA studies. Cement containing biomass ash performed better, on average, when compared with the reference landfill scenario regarding the impact to human toxicity (carcinogenic) category. Contrary, only the utilization in cement for one particular ash type (from paper sludge combustion) showed a better performance than the reference scenario for the ecotoxicity (ET) category. The impact to human toxicity carcinogenic (HTc) and ecotoxicity (ET) was mainly dominated by the leaching of Cr from landfilling of pure biomass fly ash (reference scenario) and the leaching of Ba, Cu, Cr (VI) and Zn from the second life stage of cement products (i.e., reuse of the crushed cement after service life in road base applications). However, this impact was acceptable when emissions are compared to existing EU landfill directive and regulations on the reuse of secondary materials in construction works. The novel LCA approach performed in this study, which includes impacts of leached contaminants during both the service and second life phase of cement, has shown that the reuse of biomass ash as secondary cementitious materials has a beneficial effect on the majority of the impact categories, with no unacceptable leaching risks.</p

Development of a Continuous Hydrothermal Treatment Process for Efficient Dewatering of Industrial Wastewater Sludge

Sludges from the papermaking industry represent a challenging residue stream that is difficult to dewater using conventional processes. The successful development and scale-up of innovative processes from lab- to pilot- to industrial-scale are required to tackle challenges for waste treatment, including paper sludges. Biological paper sludge was treated via a mild hydrothermal carbonization process (TORWASH&reg;) to improve dewaterability of the sludge, including long-duration, continuous testing. Initial lab-scale experiments indicated the optimal treatment temperature for sludge dewatering was 190 &deg;C. Dewaterability improved with increasing temperature, but the obtained solid yield decreased. Scaling-up to a continuous flow pilot plant required a temperature of 200 &deg;C to achieve optimum dewatering. Pilot-scale hydrothermal treatment and dewatering resulted in solid cakes with an average dry matter content of 38% and a solid yield of 39%. This study demonstrates the benefits of hydrothermal carbonization for the dewatering of biological paper sludge without the use of dewatering aids such as fiber sludge or polyelectrolytes. The results also demonstrate the successful adaptation of a lab-scale batch process to a pilot-scale continuous flow process for hydrothermal carbonization of industrial wastewater sludge