  Citation: Moure Abelenda, A.; Amaechi, C.V. Manufacturing of a Granular Fertilizer Based on Organic Slurry and Hardening Agent. Inventions 2022, 7, 26. https:// doi.org/10.3390/inventions7010026 Academic Editor: Emin Bayraktar Received: 31 December 2021 Accepted: 4 February 2022 Published: 17 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). inventions Article Manufacturing of a Granular Fertilizer Based on Organic Slurry and Hardening Agent Alejandro Moure Abelenda 1, * and Chiemela Victor Amaechi 1,2, * 1 Department of Engineering, Lancaster University, Lancaster LA1 4YW, UK 2 Standard Organisation of Nigeria (SON), 52 Lome Crescent, Wuse Zone 7, Abuja 900287, Nigeria * Correspondence: alejandro.moure.abelenda@gmail.com (A.M.A.); c.amaechi@lancaster.ac.uk (C.V.A.); Tel.: +34-650222342 (A.M.A.); +44-7946100862 (C.V.A.) Abstract: The manufacturing of a granular fertilizer based on organic slurry (OS) and sorptive materials aims to enhance the circular economy. This article describes a technology that was conceived after appraising the chemistry of the anaerobic digestate and wood ash and the synergies of combining both materials. The information available in the literature about similar materials such as cattle slurry and lime was also considered to build a better understanding of the underlying science. The processes and machinery designed were optimized from the points of view of energy and material consumption, cost of storage, transportation and land application. The system was sized to process 1 tonne of OS (97% moisture) in a 10 h batch-shift, consuming 140 kg of wood pellets and 0.55 kW of electricity for the fan blowing preheated air. The results of the market research allowed us to reach the most economically viable routes for the commercialization of granular fertilizers. Based on the financial study, an initial investment of GBP 20,000 is needed to successfully implement the value proposition and business plan. The wide adoption of the composite fertilizer improves the management of the OS and reduces the contamination of air, soil, and water derived from intensive agricultural practices. Keywords: waste valorization; fluidized bed drier; ammonia sorption; pelletization; granulation; slow release; nutrients recovery; composite fertilizer; market research; business plan 1. Introduction Recent developments of fertilizers and manures for application in farmlands have increased in recent times. This includes the manufacture of granular fertilizers, application of anaerobic digesters and utilization of manures. There are several factors that promote the implementation of manure treatment techniques, such as anaerobic digestion (AD), in farms [1]. These factors include pressure from policies and regulations; the ease of the export of manure off the farm; the production of bioenergy; the increase in the price of chemical fertilizers; the potential income due to the sale of processed products; and the control of diseases, pathogen and odors. According to Hou et al. [1], on-site manure treatment is applicable to farms with more than 50 livestock units. Technologies such as AD and drying (pelletizing) are perceived by the stakeholders of the agro-industry as only applicable at an industrial scale or farm cooperatives. However, mechanical solid–liquid separation can be implemented at a lower scale. The present study aims to promote the acceptance of technologies for the valorization and downstream processing of the OS at a farm level to avoid the unnecessary cost of storage and transportation of a large volume of OS. Currently, much more animal manure is applied to land as a soil amendment than an anaerobic digestate because of the high capital expenditure (CAPEX) and operational expenditure (OPEX) associated with the implementation of AD in the farms [1]. In 2008, the EU27 produced 259 million tonnes of municipal solid waste [2], and the organic Inventions 2022, 7, 26. https://doi.org/10.3390/inventions7010026 https://www.mdpi.com/journal/inventions