Electrolytic oxygen, only a by-product?

Electrolysis is often mentioned as a well-established and mature technology to produce hydrogen. This is an environmentally friendly process that requires water and electricity, best when this last is derived from renewable energy sources (RES). One of the main disadvantages of water electrolysis is the cost of the electrical energy, so also the hydrogen produced is more expensive than that obtained by methods based on fossil fuels, such as the conventional steam methane reforming (SMR). It is mainly for this reason that electrolysis currently accounts for only 4% of global hydrogen production; while 96% of hydrogen comes from fossil fuels (48% from natural gas, 30% from oil, and 18% from coal) [1]. Based on our previous studies [2-3], an extra revenue could be obtained by considering the amount of oxygen produced as a by-product from electrolysis: 8 kg of oxygen are produced for each kilogram of hydrogen. In agreement with considerations recently reported by IEA [4], the by-product oxygen can be used at a smaller scale in the health care sector, or at a larger scale for industrial purposes (feedstock). In this new contribution, we reverse the point of view, by considering a hypothetical enterprise or business activity (public or private) adopting an electrolysis plant to fulfil its needs of oxygen for a particular application, while the obtained hydrogen could be sold to external users to achieve additional revenues. The objective is to verify if the proposed approach is economically attractive, compared to the case when the same enterprise simply buys the oxygen from local gas distributors/resellers.