The secondary research process involved comprehensive analysis of regulatory databases, industry publications, chemical manufacturing reports, and authoritative agricultural and food safety organizations. Key sources included the US Food & Drug Administration (FDA), European Food Safety Authority (EFSA), Food and Agriculture Organization (FAO), United States Department of Agriculture (USDA), European Commission Directorate-General for Agriculture and Rural Development, Animal and Plant Health Inspection Service (APHIS), Environmental Protection Agency (EPA), European Chemicals Agency (ECHA), US Geological Survey (USGS) Mineral Commodity Summaries, International Fertilizer Association (IFA), European Feed Manufacturers' Federation (FEFAC), American Feed Industry Association (AFIA), World Health Organization (WHO) Food Additives Series, Codex Alimentarius Commission, National Agricultural Statistics Service (NASS), Eurostat Agricultural Statistics, and national agricultural ministry reports from key markets.
Production statistics, regulatory approval data, additive safety studies, agricultural trends, and market landscape analysis for phosphoric acid-based and hydrochloric acid-based production methods across food & beverage, animal feed, pharmaceutical, and agricultural applications were gathered from these sources.