Knowledge mapping for a secure and sustainable hemp industry : a systematic literature review

As a versatile and multipurpose plant, hemp (Cannabis sativa L.) possesses immense potential for its application in nutraceuticals, food and nutrition, fibre, and construction material. However, its broader industrial potentials are hindered by the lack of sufficient knowledge on varietal differences, phytochemical properties, food and fibre processing techniques, bioenergy application and valorisation of whole plant, clinical evidence, and standardised quality control mechanisms. In this context, we systematically reviewed 101 reviews and 655 research papers on hemp to map what we already know and what we still need to know about hemp, across its supply chain; from cultivar selection through production to end use. We reviewed the literature based on major themes and sub-themes. Existing literature spanned 33 sub-themes of hemp, which can be classified under five broad themes: production, material, health, futures, and research and education. The ‘material’ theme (42%) was the most researched, followed by ‘production’ (27%) and ‘health’ (19%). At the sub-theme level, one-fifth of the research articles covered fibre and composite material (n = 139), followed by phytochemical analysis and potency testing (n = 45), hempcrete and construction applications (n = 43), and germination and plantation techniques (n = 41). More than half of the selected research articles on hemp were published in the last three years (2020–2022), concentrated mainly in North America, Europe, and China. Cannabidiol, fibre, and seed oil were considered as the quick wins of hemp industry (hemp champions). Based on our review, we have discussed various research gaps and research priorities across the supply chain, beginning from early detection of hemp breed to valorisation of hemp hurd and industrial residue to address opportunities and challenges for the industrial development of major hemp products.