Green electrochemistry and electrolytic hydrogen production: opportunities for the pig industry

G. Lourinho, P. Brito, L. Rodrigues
C3i (Interdisciplinary Coordination for Research and Innovation), Polytechnic Institute of Portalegre, Campus Politécnico, 10, 7300-555 Portalegre, Portugal, Tel/Fax: +351245301592, +351245300291; E-mail: glourinho@gmail.com

Introduction

The economic activities associated with intensive pig farming require the use of substantial amounts of energy and create significant pressure on the environment, especially in the form of water pollution. Electrochemistry is naturally suited to face both issues with the possibility of coupling pig manure treatment and electrolytic hydrogen production Jiang 2008. During electrochemical treatment of manure, oxidation of organic compounds takes place at the anode, while a reduction occurs at the cathode resulting in hydrogen evolution. There are several environmentally favorable features of electrochemical transformations which conform with the principles of green chemistry: a) electrons are intrinsically clean reagents; (b) most of the reactions take place at mild conditions which reduces safety concerns; and c) electrochemistry is flexible enough to treat various organic, inorganic and biochemical pollutants Ibanez 2014. In this paper, a preliminary estimation of the potential for electrolytic hydrogen (H2) production in a pig farm is made, taking advantage of the surplus energy generated from biogas CHP. The main on farm end use for the produced H2 is in fuel cell powered farm vehicles, replacing tractors powered by diesel fuel

Experimental

To calculate the potential for H2 production via water electrolysis at a farm level in Portugal, we (a) estimated the surplus power available from biogas CHP (165kWe gas engine, 8000 hours) for the electrolysis of pig manure; and (b) calculated H2production from the power available considering a PEM electrolyzer with 75% efficiency based on HHV of H2 and 95% availability. In 2015, farm’s annual energy consumption was 718.525 kWh/year of electricity and 34.613 L of diesel fuel.

Results and discussion

The results from the application of the described methodology are summarized in Table I. Total power available for electrolytic H2 production is estimated to be 601.475 kWh/year when considering a biogas CHP system of 165kWe. Accordingly, theoretical hydrogen potential is 10.877 kg/year. Taking into account the energy equivalence between energy carriers, the electrolytic H2 produced would account for the total diesel fuel consumed in the farm in 2015.
Electrolytic hydrogen potential from biogas CHP at farm level
Biogas CHP(kWh/year) Surplus electricity Hydrogen produced
1320000 601475 10877

Conclusion

This study demonstrates the feasibility of integrating hydrogen production in pig manure treatment using green electrochemical methods. Theoretical analysis has shown that the calculated potential is enough to replace total diesel demand at a farm level in Portugal. This study is encouraging that the integration of electrochemical manure treatment and hydrogen production can provide valuable opportunities of cost reduction and energy savings for the pig industry as hydrogen can be used, for example, in farm machinery powered by fuel cells.