{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T15:35:54Z","timestamp":1787585754008,"version":"build-2736575974"},"reference-count":52,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,8,23]],"date-time":"2026-08-23T00:00:00Z","timestamp":1787443200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Bioengineering"],"abstract":"<jats:p>Keratin is an abundant, recalcitrant structural protein that constitutes the primary component of several animal wastes, particularly chicken feathers. Because of their potential and availability, various technologies, such as anaerobic biodigestion, have been used to degrade keratin and transform feathers into biogas and other value-added products. However, due to their fibrous architecture and rigid structure, keratinous materials are elastic, water-insoluble, and enzymatically resistant, which makes natural degradation difficult. In this sense, before using chicken feathers as feedstock in biodigesters, the keratin in the residue must be cleaved in pretreatment steps. Whether as a single substrate or in co-digestion processes, the keratin breakdown is critical for enhancing biogas production from feathers. In this context, there is growing emphasis on developing pretreatment methods to facilitate protein hydrolysis and digestion, thereby improving biogas generation. To evaluate progress in recycling waste keratin, a bibliometric analysis of original scientific publications on the pretreatment of chicken feathers for anaerobic digestion was conducted using the Scopus database. The findings indicate that researchers apply chicken feathers in processes, including standard biodigestion, co-digestion with food waste, animal manure, and slaughterhouse waste, for biomethane and biohydrogen production. Across the evaluated studies, the pretreatment methods showed notable improvements in feather solubilization and subsequent biogas yield; however, they still encounter key limitations, including ammonia (NH3) inhibition, high chemical\/reagent costs, and high energy demand.<\/jats:p>","DOI":"10.3390\/bioengineering13090962","type":"journal-article","created":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T14:49:34Z","timestamp":1787582974000},"page":"962","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Research Progress on the Pre-Treatment of Chicken Feathers for Biogas Production"],"prefix":"10.3390","volume":"13","author":[{"given":"Isa Beatriz Concei\u00e7\u00e3o","family":"Oliveira-Alves","sequence":"first","affiliation":[{"name":"RENORBIO\u2014Northeastern Biotechnology Network, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4418-5487","authenticated-orcid":false,"given":"Hort\u00eancia E. P.","family":"Santana","sequence":"additional","affiliation":[{"name":"RENORBIO\u2014Northeastern Biotechnology Network, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-2657-7077","authenticated-orcid":false,"given":"Ingrid Vieira","family":"Fernandes","sequence":"additional","affiliation":[{"name":"RENORBIO\u2014Northeastern Biotechnology Network, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"},{"name":"CCET\u2014Center for Exact Sciences and Technology, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8625-978X","authenticated-orcid":false,"given":"Meirielly","family":"Jesus","sequence":"additional","affiliation":[{"name":"CISAS\u2014Center for Research and Development in Agrifood Systems and Sustainability, Universidade Polit\u00e9cnica de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0043-2068","authenticated-orcid":false,"given":"Joana","family":"Santos","sequence":"additional","affiliation":[{"name":"CISAS\u2014Center for Research and Development in Agrifood Systems and Sustainability, Universidade Polit\u00e9cnica de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5687-7114","authenticated-orcid":false,"given":"Fernando","family":"Mata","sequence":"additional","affiliation":[{"name":"CISAS\u2014Center for Research and Development in Agrifood Systems and Sustainability, Universidade Polit\u00e9cnica de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"},{"name":"Esta\u00e7\u00e3o Zoot\u00e9cnica Nacional, Instituto Nacional de Investiga\u00e7\u00e3o Agr\u00e1ria e Veterin\u00e1ria (INIAV), 2784-424 Vale de Santar\u00e9m, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9836-5678","authenticated-orcid":false,"given":"Samia T\u00e1ssia Andrade","family":"Maciel","sequence":"additional","affiliation":[{"name":"CCET\u2014Center for Exact Sciences and Technology, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1550-6341","authenticated-orcid":false,"given":"Denise Santos","family":"Ruzene","sequence":"additional","affiliation":[{"name":"RENORBIO\u2014Northeastern Biotechnology Network, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"},{"name":"CCET\u2014Center for Exact Sciences and Technology, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"},{"name":"CISAS\u2014Center for Research and Development in Agrifood Systems and Sustainability, Universidade Polit\u00e9cnica de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"},{"name":"PROBIO\u2014Graduate Program in Biotechnology, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2266-4428","authenticated-orcid":false,"given":"Daniel Pereira","family":"Silva","sequence":"additional","affiliation":[{"name":"RENORBIO\u2014Northeastern Biotechnology Network, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"},{"name":"CCET\u2014Center for Exact Sciences and Technology, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"},{"name":"CISAS\u2014Center for Research and Development in Agrifood Systems and Sustainability, Universidade Polit\u00e9cnica de Viana do Castelo, 4900-347 Viana do Castelo, Portugal"},{"name":"PROBIO\u2014Graduate Program in Biotechnology, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"},{"name":"PPGPI\u2014Graduate Program in Intellectual Property Science, Federal University of Sergipe, S\u00e3o Crist\u00f3v\u00e3o 49107-230, SE, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,23]]},"reference":[{"key":"ref_1","unstructured":"OECD-FAO (2025). 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