Biohydrogen production

4.4.1 Introduction

In this article, it will be covered only a discussion on the biohydrogen process, once they are straight connected with the main focus of this article. However, it is necessary to have a clear idea of the existing hydrogen technologies, mainly, its cost, in order to understand the potential for the biological hydrogen production technologies. Also it is important to recognize that hydrogen can be produced straight from biomass, without intensive technology use, including also, decentralized production.

Hydrogen is an energy carrier that could be produced actually by different processes like, natural gas reforming, coal gasification, nuclear, water electrolysis, thermal water splitting and biomass, photo-electrolysis and biological processes [53]. Hydrogen can be used for power generation or used as a transport fuel, mainly in association with fuel cells. Natural gas and coal are the two most current and cheapest sources of H2 production. These processes release CO2, and so, capture and storage are required to reduce the CO2- emissions. Decentralized production of Hydrogen is the best choice for market uptake and for avoiding distribution costs due to the need of infrastructure.

According to IEA — Energy Technology Essentials [53] hydrogen could gain market share in the transport sector if costs of production, distribution and end-use technologies decrease in consonance with the expectations, as well as, if strong policies are placed in order to reduce CO2 emissions. Under adequate circumstances, hydrogen could be entering the market around the year 2020. For that, it should be powering around 700 million fuel cell driven vehicles by 2050, which means, 30% of the projected global fleet [53]. According to IEA report, costs varies, depending of sources and raw materials costs. In summary, hydrogen from electrolysis costs above $30/GJH2, once considering electricity cost at $35/MWh with 80% efficiency; hydrogen from steam methane reforming (SMR) costs ranges between $10-$15/GJH2, considering natural gas price between $6-$9/GJ; coal gasification costs range between $7-$10/GJH2, assuming $1- $1.5/GJ for coal price, and $35-40/MWh for electricity with 45% electrical efficiency; hydrogen from nuclear using its high temperature heat costs about $10-$20/GJ, and from megawatt-scale concentrating solar power systems $20-30/GJ.

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