Blending based optimisation and pretreatment strategies to enhance anaerobic digestion of poultry manure

This is the accepted manuscript of the following article: Rodriguez-Verde, I., Regueiro, L., Lema, J., & Carballa, M. (2018). Blending based optimisation and pretreatment strategies to enhance anaerobic digestion of poultry manure. Waste Management, 71, 521-531. doi: 10.1016/j.wasman.2017.11.002 © 2018 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Anaerobic digestion of poultry manure is limited by the excessive levels of nitrogen and the high concentration of dry matter. These limitations are usually overcome either by applying procedures to remove nitrogen or by employing pretreatments that allows to solubilise organic matter. In this work, the treatment of poultry manure was enhanced by co-digestion with pig manure through the methodological determination of optimal mixtures combined together with a thermochemical pretreatment coupled to ammonia stripping. The optimum poultry-pig mixture, resulting in a 24%:76% (volume basis) poultry-pig manure, was determined by applying a methodology based on linear programming which calculates the proportions of the blend which returns the maximum methane production while keeping a stable process. Pretreatment batch experiments, consisting of increasing both temperature and pH simultaneously with ammonia stripping process was optimised for a temperature of 90 °C and a pH of 10 resulting in a nitrogen removal efficiency of 72% and a 1.2-fold higher methane production in comparison to the unpretreated mixture. Continuous anaerobic co-digestion of pretreated optimum mixture enhanced the COD removal efficiency by 37% when compared with the treatment of unpretreated feedstock (37% vs 27%, respectively). This study indicates that combining blending optimisation of substrates, thermochemical pretreatments and ammonia stripping procedures prior to anaerobic co-digestion becomes a good strategy to overtake the limitations offered by solid- and nitrogen-rich substrates, such as poultry manureThis research was supported by the European Comission by ManureEcoMine project (ENV.213.6.3-2) and by CDTI through SmartGreenGas project (2014-CE224). The authors belong to CRETUS (AGRUP2015/02) and to the Galician Competitive Research Group GRC 2013-032, both programme co-funded by FEDERS

Effect of oxygen on the microbial activities of thermophilic anaerobic biomass

Low oxygen levels (ug O2 L-1) in anaerobic reactors are quite common and no relevant consequences are expected. On the contrary, higher concentrations could affect the process. This work aimed to study the influence of oxygen (4.3 and 8.8 mg O2 L-1, respectively) on the different microbial activities (hydrolytic, acidogenic and methanogenic) of thermophilic anaerobic biomass and on the methanogenic community structure. Batch tests in presence of oxygen were conducted using specific substrates for each biological activity and a blank (with minimum oxygen) was included. No effect of oxygen was observed on the hydrolytic and acidogenic activities. In contrast, the methane production rate decreased by 40% in all oxygenated batches and the development of active archaeal community was slower in presence of 8.8 mg O2 L-1. However, despite this sensitivity of methanogens to oxygen at saturation levels, the inhibition was reversible.This research was supported by the European Community Seventh Framework Programme under Grant Agreement nº 603744 (ManureEcoMine project), by the Spanish Ministry of Economy and Competitiveness through CDTI (SmartGreenGas project, 2014-CE224) and the Ramón y Cajal contract (RYC-2012- 10397). The authors belong to the Galician Competitive Research Group GRC 2013-032, programme co-funded by FEDERS

Presence does not imply activity: DNA and RNA patterns differ in response to salt perturbation in anaerobic digestion

Background The microbial community in anaerobic digestion is mainly monitored by means of DNA-based methods. This may lead to incorrect interpretation of the community parameters, because microbial abundance does not necessarily reflect activity. In this research, the difference between microbial community response on DNA (total community) and RNA (active community) based on the 16S rRNA (gene) with respect to salt concentration and response time was evaluated. Results The application of higher NaCl concentrations resulted in a decrease in methane production. A stronger and faster response to salt concentration was observed on RNA level. This was reflected in terms of microbial community composition and organization, as richness, evenness, and overall diversity were differentially impacted. A higher divergence of community structure was observed on RNA level as well, indicating that total community composition depends on deterministic processes, while the active community is determined by stochastic processes. Methanosaeta was identified as the most abundant methanogen on DNA level, but its relative abundance decreased on RNA level, related to salt perturbation. Conclusions This research demonstrated the need for RNA-based community screening to obtain reliable information on actual community parameters and to identify key species that determine process stabilityThis research was supported by the Spanish Ministry of Economy and Competitiveness and COMPLETE BELGIUM through REWATER project (EU ERANET NEWINDIGO—DST. PRI-PIMNIN-2011-1487). Jo De Vrieze is supported as postdoctoral fellow from the Research Foundation Flanders (FWO-Vlaanderen). Ruben Props is supported by Ghent University (BOFDOC2015000601) and the Belgian Nuclear Research Centre (SCK CEN). Leticia Regueiro, Juan M. Lema, and Marta Carballa belong to CRETUS (AGRUP2015/02) and to the Galician Competitive Research Group (GRC 2013-032)S

Bacterial community dynamics in long‐term operation of a pilot plant using aerobic granular sludge to treat pig slurry

This is a Post-print version of the articleAerobic granular sludge represents an interesting approach for simultaneous organic matter and nitrogen removal in wastewater treatment plants. However, the information about microbial communities in aerobic granular systems dealing with industrial wastewater like pig slurry is limited. Herein, bacterial diversity and dynamics were assessed in a pilot scale plant using aerobic granular sludge for organic matter and nitrogen elimination from swine slurry during more than 300 days. Results indicated that bacterial composition evolved throughout the operational period from flocculent activated sludge, used as inoculum, to mature aerobic granules. Bacterial diversity increased at the beginning of the granulation process and then declined due to the application of transient organic matter and nitrogen loads. The operational conditions of the pilot plant and the degree of granulation determined the microbial community of the aerobic granules. Brachymonas, Zoogloea and Thauera were attributed with structural function as they are able to produce extracellular polymeric substances to maintain the granular structure. Nitrogen removal was justified by partial nitrification (Nitrosomonas) and denitrification (Thauera and Zoogloea), while Comamonas was identified as the main organic matter oxidizing bacteria. Overall, clear links between bacterial dynamics and composition with process performance were found and will help to predict their biological functions in wastewater ecosystems improving the future control of the processThis work has been financed by FISHPOL (CTQ2014-55021-R) and GRANDSEA (CTM2014-55397-JIN) projects from the Spanish Government and co-funded by FEDER. The authors belong to the Galician Competitive Research Group GRC 2013-032, programme co-funded by FEDER, and CRETUS (AGRUP2015/02)S

A circular economy framework for seafood waste valorisation to meet challenges and opportunities for intensive production and sustainability

There is a growing concern among societies and consumers over food security and the sustainability of food production systems. For seafood, it has been highly advocated as a healthy food source and its sustainability credentials. However, the increasing global demand for seafood and the need to supply the quantities are creating sustainability issues, e.g., the importation of plant and marine proteins for aquafeed production. Consequently, there is a necessary need to analyse the supply chain and life cycle of these systems to determine their sustainability merits and how to enhance them. The circular economy (CE) aims to reduce processing by-product underutilisation, increase the rate of reuse, and reduce pressure on natural resources and systems. For seafood, there are large quantities of biomass that are being lost through bycatch/discards, waste from aquaculture (e.g., sludge and wastewater), and by-products generated through processing (e.g., trimmings and offal). These can all be valorised for the generation of feeds, value-added products, or further food production. This review will focus on seafood by-products generated during the processing into consumer products, and the current methods that could be used to manage or treat these waste streams. The review presents a stepwise framework that outlines valorisation opportunities for seafood by-products. This framework can enable producers, operators, regulators, and investors to integrate with the principles of the CE with the consideration of achieving economic viability. The challenges of seafood loss due to climate change and emerging recycling strategies will also need to be considered and integrated into the valorisation pathways. Communication, education, and engagement with stakeholders are key to transitioning to a circular economy. Where increase awareness and acceptance will create drivers and demand for seafood by-product valorisation. Overall, the impact of such a circular production system will potentially lead to higher production efficiency, reduce demand for natural resources, and greater seafood production. All of which addresses many of the United Nation's Sustainable Development Goals by contributing towards future food security and sustainability.This work was supported by the EAPA_576/2018 NEPTUNUS project. The authors would like to acknowledge the financial support of Interreg Atlantic Area. A.H.L Wan was co-funded under the HYDROfish project (2019–2022) which was funded under the Disruptive Technologies Innovation Fund (DTIF), established under Project Ireland 2040, run by the Department of Enterprise Trade and Employment with administrative support from Enterprise Ireland. His opinions expressed are his own. The authors would also like to thank Matt Bell for his editorial assistance

Life cycle assessment of fish and seafood processed products: a review of methodologies and new challenges

Life cycle assessment (LCA) has been widely applied in many different sectors, but the marine products and seafood segment have received relatively little attention in the past. In recent decades, global fish production experienced sustained growth and peaked at about 179 million tonnes in 2018. Consequently, increased interest in the environmental implications of fishery products along the supply chain, namely from capture to end of life, was recently experienced by society, industry and policy-makers. This timely review aims to describe the current framework of LCA and its application to the seafood sector that mainly focused on fish extraction and processing, but it also encompassed the remaining stages. An excess of 60 studies conducted over the last decade, along with some additional publications, were comprehensively reviewed; these focused on the main LCA methodological choices, including but not limited to, functional unit, system boundaries allocation methods and environmental indicators. The review identifies key recommendations on the progression of LCA for this increasingly important sustaining seafood sector. Specifically, these recommendations include (i) the need for specific indicators for fish-related activities, (ii) the target species and their geographical origin, (iii) knowledge and technology transfer and, (iv) the application and implementation of key recommendations from LCA research that will improve the accuracy of LCA models in this sector. Furthermore, the review comprises a section addressing previous and current challenges of the seafood sector. Wastewater treatment, ghost fishing or climate change, are also the objects of discussion together with advocating support for the water-energy-food nexus as a valuable tool to minimize environmental negativities and to frame successful synergies.This work was supported by the EAPA_576/2018 NEPTUNUS project. The authors would like to acknowledge the financial support of Interreg Atlantic Area. Ana Cláudia Dias and Paula Quinteiro acknowledge FCT/MCTES for the financial support to CESAM (UIDB/50017/2020 + UIDP/50017/2020), through national funds, and to the research contracts CEECIND/02174/2017 and CEECIND/00143/2017, respectively