Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2023
Abstract
Anaerobic digestion (AD) can be used as a stand-alone process or integrated as part of a larger biorefining process to produce biofuels, biochemicals and fertiliser, and has the potential to play a central role in the emerging circular bioeconomy (CBE). Agricultural residues, such as animal slurry, straw, and grass silage, represent an important resource and have a huge potential to boost biogas and methane yields. Under the CBE concept, there is a need to assess the long-term impact and investigate the potential accumulation of specific unwanted substances. Thus, a comprehensive literature review to summarise the benefits and environmental impacts of using agricultural residues for AD is needed. This review analyses the benefits and potential adverse effects related to developing biogas-centred CBE. The identified potential risks/challenges for developing biogas CBE include GHG emission, nutrient management, pollutants, etc. In general, the environmental risks are highly dependent on the input feedstocks and resulting digestate. Integrated treatment processes should be developed as these could both minimise risks and improve the economic perspective.
Abstract
No abstract has been registered
Abstract
Manure management is a significant source of methane (CH4) and ammonia (NH3), and there is an urgent need for strategies to reduce these emissions. More frequent export of manure for outside storage can lower gaseous emissions from housing facilities, but the longer residence time may then increase emissions during outside storage. This study examined CH4 and NH3 emissions from liquid pig manure (pig slurry) removed from the in-house slurry collection pits at three different frequencies, i.e., three times per week (T2.3), once per week (T7), or once after 40 days (T40, reference). The slurry from treatments T2.3 and T7 was transferred for outside storage weekly over four weeks, and slurry from treatment T40 once after 40 days, in connection with summer and winter production cycles with growing-finishing pigs. The slurry was stored in pilot-scale storage tanks with solid cover and continuous ventilation. Compared to T40, the treatments T2.3 and T7 increased CH4 emissions during outside storage, but in-house emissions were reduced even more, and the net effects on total CH4 emissions from manure management (housing unit and outside storage) were reductions of 18–41% in summer and 53–83% in winter. The frequent slurry export for outside storage led to more NH3 emissions, except for the treatment T2.3, which has slurry funnel inserts beneath the slatted floor. Measurements of in-vitro CH4 production rates suggested that shorter residence time for slurry in pig houses delayed the development of active methanogenic populations, and that this contributed to the reduction of CH4 emissions.
Authors
Yeqing Li Shasha Yu Xingru Yang Yijing Feng Liming Dong Yi Zhang Lu Feng Mahmoud Mazarji Junting PanAbstract
In the anaerobic digestion (AD) process, the effects of humic acid (HA) derived from different feedstocks on AD are influenced by the variations in their structural composition and oxygen-containing functional groups. Thus, clarifying the structural differences of HA obtained from different feedstocks is crucial for understanding their impact on AD. In this study, the structure of five humic acids (HAs) derived from liquid digestate, food waste, silage corn straw, lignite and commercial HA, and their effects on AD were investigated. The study found that HA from food waste had more carboxyl groups, while straw-derived HA had more phenolic hydroxyl groups. Both types of HA had higher aromaticity and humification degree and showed significant inhibition effect on AD. HA from food waste had an average methanogenic inhibition rate of 43.5 % with 1 g/L HA added. In addition, commercial HA and HA derived from lignite had similar functional group types and aromaticity, with an average methanogenic inhibition rate of about 20 %. The study revealed that HAs with more carboxyl groups exhibited greater effectiveness in inhibiting AD, thereby confirming the influence of HA structures derived from different feedstocks on AD. In conclusion, this study provides valuable insights into the mechanism of HA effect on AD and offers guidance for future research focused on enhancing AD efficiency.
Abstract
No abstract has been registered
Abstract
The treatment of organic waste (OW) by anaerobic digestion (AD) conforms to the concept of sustainable development. But AD is facing the issue of low conversion rate. In this work, the photo-AD system using visible light (LED lamp) as the source was constructed and the performances and mechanism of N-doped carbon quantum dots (NCQD) were explored in the system for the first time. The results showed that 0.5 g/L NCQD promoted a 23.1 % increase in cumulative CH4 yield in the photo-AD system. Microbial analysis results showed that in photo-AD with NCQD, the dominant strain was Methanosarciniales, with an abundance of 69.0 %. Microbial activity and structural integrity tests showed that the microorganisms were not damaged by free radicals. In addition, NCQD increased the redox peak intensity of the CV curve and increased photocurrent intensity of photo-AD. Furthermore, it promoted an increase of 18.2 % (0.26 ± 0.03 μmol/mL) in ATP concentration. The photoelectrochemical analysis and quantitative analysis of functional genes results indicated that NCQD mainly promoted methanogenesis by providing photoelectrons. This promotion mechanism increased the copynumber (61,652.8 g−1) of EchA in photo-AD, rather than Vht and Hdr related to cytochrome. This work provided new strategies for the enhancement of AD and clarified potential mechanisms.
Authors
Yi Zhang Yun Zhao Yijing Feng Yating Yu Yeqing Li Jian Li Zhonghao Ren Shuo Chen Lu Feng Junting Pan Hongjun Zhou Yongming HanAbstract
Industrial-scale garage dry fermentation systems are extremely nonlinear, and traditional machine learning algorithms have low prediction accuracy. Therefore, this study presents a novel intelligent system that employs two automated machine learning (AutoML) algorithms (AutoGluon and H2O) for biogas performance prediction and Shapley additive explanation (SHAP) for interpretable analysis, along with multiobjective particle swarm optimization (MOPSO) for early warning guidance of industrial-scale garage dry fermentation. The stacked ensemble models generated by AutoGluon have the highest prediction accuracy for digester and percolate tank biogas performances. Based on the interpretable analysis, the optimal parameter combinations for the digester and percolate tank were determined in order to maximize biogas production and CH4 content. The optimal conditions for the digester involve maintaining a temperature range of 35–38 °C, implementing a daily spray time of approximately 10 min and a pressure of 1000 Pa, and utilizing a feedstock with high total solids content. Additionally, the percolate tank should be maintained at a temperature range of 35–38 °C, with a liquid level of 1500 mm, a pH range of 8.0–8.1, and a total inorganic carbon concentration greater than 13.8 g/L. The software developed based on the intelligent system was successfully validated in production for prediction and early warning, and MOPSO-recommended guidance was provided. In conclusion, the novel intelligent system described in this study could accurately predict biogas performance in industrial-scale garage dry fermentation and guide operating condition optimization, paving the way for the next generation of intelligent industrial systems.
Abstract
Biowaste is becoming a significant category in the global energy mix to mitigate the negative impacts of burning fossil fuels. The aim of this review paper was to investigate the potential, conversion mechanisms, benefits, and policy gaps related to the utilization of solid biowaste resources as renewable, clean, and affordable energy sources. Thus, a systematic review approach was employed to undertake a comprehensive analysis of the studies that dealt with solid biowaste resources for energy recovery. This review paper was conducted from November 2022 to June 2023. The relevant literature was searched using databases from scholarly journal publishers, online search engines, and websites. A total of 82 studies were determined to be eligible from 659 records. Ethiopia has a huge potential for biowaste resources, with an annual generation potential of 18,446.4 MJ per year. The multifaceted advantages associated with biowaste-to-energy conversion such as clean energy production, waste management, forest conservation, greenhouse gas emission reduction, and maintaining soil fertility using the digestate left after anaerobic digestion were mentioned. This review highlights various conversion technologies for converting solid biowastes into valuable forms of energy, such as thermochemical, biochemical, and physico-mechanical techniques. It also investigated the value-added products of the Solid Biowastes-to-Energy (SBWtoE) process, including bio-oil, syngas, bioethanol, biodiesel, biomethane, bio-briquettes, and pellets, with applications ranging from transportation to power generation. Furthermore, this review addresses the multifaceted challenges associated with implementing a circular economy, emphasizing the need to overcome policy, technological, financial, and institutional barriers. These efforts are crucial for harnessing the growing biowaste resources in Ethiopia, ultimately promoting sustainable and cost-effective energy production while advancing the nation's environmental objectives.
Abstract
No abstract has been registered
Authors
Lu FengAbstract
No abstract has been registered