Chapter 21 - Biohydrogen Production from Bio-oil

Abstract

Biohydrogen can be produced through thermochemical conversion, electrohydrogenesis, and biological conversion of biomass. This chapter focuses on thermochemical conversion of biomass for production of biohydrogen. Thermochemical conversion process includes gasification of biomass and bio-oil. Gasification of biomass in limited supply of oxygen results in the formation of syngas which is a mixture of carbon monoxide, carbon dioxide, methane, and hydrogen. One of the direct pathways is by converting syngas to biohydrogen. Syngas can be converted to biohydrogen by steam reforming. The production of biohydrogen from bio-oil includes two key steps. First step is the production of bio-oil by fast pyrolysis of biomass and the second step is reforming of bio-oil to biohydrogen. If biohydrogen production plant is integrated with the bio-oil production plant, there is noneed to transport bio-oil. If the biohydrogen production plant is located faraway from the bio-oil production plant, bio-oil needs to be transported by truck or pipeline to the biohydrogen plant. Steam is required in the biohydrogen production process in two key steps. First, steam is required during bio-oil reforming. The steam required for this step is mainly for providing heat for the reforming process as it is an endothermic process. The amount of steam required dictates the extent of biohydrogen production. Steam is also required in the water-gas shift reaction of syngas to biohydrogen. Steam for these two steps could be generated by cooling of the organic vapors produced during the fast pyrolysis of biomass to produce bio-oil. This steam could be generated in a heat recovery steam generation unit. The steam required for these two steps could also be produced from an external source either by combusting biomass, produced bio-oil or any other fossil fuel.