Multi-purpose Crops: Hemp, a Nature Based Solution Towards Sustainable Agriculture and Water Productivity

There is a growing interest in multipurpose crops that are capable of delivering improved biomass usability while also being a source of non-food oils, biomaterials, nutraceutical products, and other valuable bio-products that can benefit society as a whole. Hemp is among these valuable multipurpose crops, considering it is a source of raw materials for several production chains in food and non-food industries.

Industrial hemp is considered a unique crop with a centuries-long history of widespread uses. On the other hand, during the past seventy years, hemp – growers have been facing multiple constraints, unrelated to agro-technical challenges. The difficulty of enforcing separate rules for the cultivation of industrial hemp and the variety used to produce marijuana led to severe cultivation restrictions. As a result, the full development of the multi-functional potential of hemp has been hampered by a combination of regulatory frameworks and socio-economic misconceptions. Thus, effective dissemination of clear and reliable information requires urgent attention (Young, 2005).  

Recent literature documents a worldwide revival of interest in hemp cultivation (Fike, 2016) and the potential of hemp for multi-functional uses, such as supplying raw materials for a diverse range of consumer products. Approximately more than 25,000 products in nine submarkets are derived from hemp raw materials including agriculture, textiles, recycling, automotive, furniture, food and beverages, paper, construction materials, and personal care which are made with hemp (Johnson, 2018; Morin-Crini et al, 2019). 

To make hemp an economically viable industrial crop, it is necessary to better identify how to use the entire plant (i.e., its uses, markets, and technologies). In general, dual-use crop production seems to be the most economically viable solution. 

The impact of the right choice of intended end-products, on the basis of the initial raw materials available, can be illustrated by a simple example. Let us take a hemp seed dry biomass of 25 kg. This can be used to produce 4 litres of hemp oil (i.e., the 15% for “oil food”) and 17.5 kg for “hemp flour” (i.e., 70% of dry biomass) (Tedeschi et al. 2022). One hectare of hemp provides the same amount of raw material for paper as 4 hectares of trees. Therefore, knowing the availability of total biomass and the various biomass fractions (leaves, stems, seeds, etc) needed as raw material for the different commercial products can allow for estimating the end products obtainable from hemp cultivation. 

Global warming and the expected population growth will lead, even in the Mediterranean area, to a decrease in water availability and an increase in the risks of salinization of the lands. In this regard, Cheng et al. (2016), Przemyslaw et al. (1995), underline that hemp can adapt to saline and alkali soils in marginal areas. Later Hu et al 2018 and Lixandru et al. (2007) evaluated the hemp response to salinity and these few studies classified hemp as moderately sensitive. Besides its sensitivity to salinity, the crop water productivity (CWP) of hemp under salinity shows a lower CWP with increasing salinity, especially for the highest salinity level (S₃=7.03 dSm^-1) see table below.  

Table- Crop water productivity (CWP) evaluated for the different hemp fraction produced: seed (CWPs), fiber (CWPf), and hurd (CWPh) in relation to the electrical conductivity (ECe) of the soil profile salinity in the layer 0.0-0.9 m (extracted by Tedeschi et al 2022 in press).

To overcome the agricultural challenges in marginal areas, where the cultivation of high-income food plants is not feasible, we will need to rethink selected plants in the future. Therefore, emphasis should be directed towards more eco-friendly crops that require low inputs, adapt to a wide range of climates, and can provide raw materials for a wide range of marketable products.

References

• Cheng, X. ; Deng, G. ; Su, Y. ; Liu, J.J. ; Yang, Y. ; Du, G.H. Protein mechanisms in response to NaCl-stress of salt-tolerant and salt-sensitive industrial hemp based on iTRAQ technology. Ind Crops Prod 2016, 83, 444–452. 
• Young,  E.M. Revival of Industrial Hemp:A systematic analysis of the current global industry to determine limitations and identify future potentials within the concept of sustainability.  Thesis submitted in partial fulfillment of the requirements of the Master’s Degree of International Environmental Science Lund University, 2005, Sweden. 
• Fike, J. Industrial Hemp: Renewed Opportunities for an Ancient Crop, Critical Reviews in Plant Sciences, 2016, 35:5-6, 406-424.
• Johnson, R. Hemp as an Agricultural Commodity. Congressional Research Service 7-5700 ww.crs.gov RL32725, 2018 June 22. 
• Lixandru, G.; Filipov, F.; Dumbravă, I. Plant tolerance to soil salinity in the conception of the Iaşi School of Soil Science. Cercetări Agronomice în Moldova 2007.40 (2), 15-31.
• Morin-Crini, N.; Loiacono, S.; Placet, V.;  Torri, G.; Bradu, C.;   Kostić, M.; Cosentino, C.; Chanet, G.; Martel, B.; Lichtfouse, E.; Crini, G. Hemp‑based adsorbents for sequestration of metals: a review. Environ. Chemistry Letters, 2019, 17: 393-408.
• Przemyslaw, B.; Grabowska, L.; Mankowski, J. Recultivation of degraded areas through cultivation of hemp. In: Proceedings of Biorohstoff Hanf Symposium, Frankfurt am Main, Germany, 1995, 2-5 Murch.
• Tedeschi, A.; Cerrato, D., Menenti, M. Is hemp a better option than maize for sustainable agriculture under saline irrigation water? Agronomy, 2022 in press.