Toward a zero-waste model: Potential for microorganism growth on agricultural waste products in Hawaii

Authors: HEUREUX, ANA - Food And Agriculture Organization Of The United Nations-European Commission For The Control Of Foot; Matsumoto Brower, Tracie; Keith, Lisa

Submitted to: Algal Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2022
Publication Date: 2/2/2022
Citation: Heureux, A.M., Matsumoto Brower, T.K., Keith, L.M. 2022. Toward a zero-waste model: Potential for microorganism growth on agricultural waste products in Hawaii. Algal Research. 62. Article 102640. https://doi.org/10.1016/j.algal.2022.102640.
DOI: https://doi.org/10.1016/j.algal.2022.102640

Interpretive Summary: Microorganisms hold vast potential to address the growing demand for sustainable fuel, feed and other bioproducts. In Hawaii, over 85% of all goods (including food and petroleum) are imported, making the need for renewable products more pressing. The zero-waste model aims to use agricultural waste products from Hawaii, including those unmarketable due to post-harvest damage or pests, as the carbon substrate for the growth of heterotrophic microorganisms. The microbial end-product can then be used as a source of high protein or lipid (fat), depending on the species and substrate, for downstream production of biodiesel or other bioproducts. In this study, we demonstrate the growth of four heterotrophic microorganisms on three waste products and explore optimization of substrate/organism combinations for further investigation. In addition, this study measures proximate composition of the end-products to compare the relative percentage of key components of the dry material. The results of this study prove the viability of the zero-waste model and propose a model for future scale-up of microorganism growth on waste substrates in Hawaii and beyond.

Technical Abstract: Microorganisms hold vast potential to address the growing demand for sustainable fuel, feed and other bioproducts. In Hawaii, over 85% of all goods (including food and petroleum) are imported, making the need for renewable products more pressing. The zero-waste model aims to use agricultural waste products from Hawaii, including those unmarketable due to post-harvest damage or pests, as the carbon substrate for the growth of heterotrophic microorganisms. The microbial end-product in turn can be used as a source of high protein or lipid (fat), depending on the species and substrate, for downstream production of biodiesel or other bioproducts. With the view to expand upon the zero-waste model piloted on the microalgae Chlorella protothecoides grown on papaya culls, this study investigates the growth of 4 microorganisms on 3 different growth substrates. The substrates tested, all waste products, include off-grade culled papaya, off-grade Okinawan sweet potato and crude glycerol, a byproduct of biofuel synthesis from Pacific Biodiesel (Keaau, HI). In this study, we demonstrate the viability of microorganism growth on all three waste products and explore optimization of substrate/organism combinations for further investigation. In addition, this study measures proximate composition of the end-products to compare the relative percentage of key components of the dry material (i.e. protein, fat, fiber, ash, etc.). The results of this study prove the viability of the zero-waste model and propose a model for future scale-up of microorganism growth on waste substrate in Hawaii, and more broadly.