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The high water use efficiency of CAM plants makes them excellent candidates for cultivation over areas where rainfall is too little or evapotranspiration too high for the cultivation of C₃ or C₄ crops. Such areas may well expand in future. Examples include the production of pineapple, Ananas comosus, for consumption, of Opuntia spp. for animal fodder, of sisal, Agave sisalana, for fibre, and of Agave tequilana for the alcoholic beverages tequila and mescal (Borland et al., 2009). In addition, species of Agave are grown for both liquid and gaseous biofuels and indeed other products such as enzymes and lactic and succinic acid (Perez‐Pimienta et al., 2017). Current quantities grown are small compared with the most common alternatives based around corn, sugar cane and wheat, and most of this is in Mexico. However, the much greater productivity of Agave (Figure 3.18), and the high water use efficiency it derives from its CAM metabolism, highlights its great potential for the future.

Figure 3.18 Agave species (CAM plants) exhibit high productivity due to their high water use efficiency. Comparison of the productivities of various species of Agave (double entries reflect separate studies) and four selected bioenergy feedstocks (raw products for the production of biofuels). Corn stover consists of the remains of plants left in the field after corn (Zea mays) has been harvested. Sugarcane bagasse is the fibrous matter than remains after sugarcane (Saccharum spp.) has been crushed to extract its juice.

Source: After Perez‐Pimienta et al. (2017).