Steam gasification of marine biomass and its biochars for hydrogen-rich gas production

In this study, steam gasifications of a kind of marine biomass, i.e., Zostera marina (eelgrass), and the biochars derived from pyrolysis of it were carried out for the biohydrogen production in a fixed-bed reactor. The effects of reaction temperature and water injection rate on the hydrogen production were investigated. In order to understand the effect of sea salts attached on the surface of eelgrass for the hydrogen production, the eelgrass washed by water (washed-eelgrass) was also used as the feedstock. It was observed that hydrogen productions from the gasification of washed-eelgrass as well as its biochar were higher than those of raw eelgrass and its biochar, indicating that the impurities of raw eelgrass had a negative effect on the hydrogen production. The biochar derived from the pyrolysis of washed eelgrass at 550 °C had the largest amount of hydrogen yield at the gasification temperature of 850 °C with a water injection rate of 0.15 g/min. It was found that both the hydrogen production and reaction rates were enhanced by mixing washed-eelgrass biochar obtained at 350 °C with the calcined seashells at a weight ratio of 1 to 2, especially at the gasification temperature of 650 °C. Meanwhile, in the presence of the calcined seashell, CO2 content decreased sharply whereas the hydrogen yield had no obvious increase.