Zero fossil energy use concept of a factory operating in the food industry

Abstract

The limited availability of fossil energy resources and constantly increasing energy prices motivate today's companies to search for new solutions to provide for the energy needs of their production processes. These new solutions should be not only cheaper compared to the fossil energy resources currently in use, but also sustainable in the long term. In the case of the food industry, processing generates large quantities of by-products with high organic matter content. These byproducts can be used to produce bio-energy. This study shows a byproduct-based energy supply concept of a food factory with extremely high energy demand, the Sugar Factory of Kaposvár. The main goal of this study is to work out a biogas production system based on industrial byproducts that could cover the total energy demand of sugar production. The concept is based on three pillars. The first pillar of the system is the enlargement and intensification of two extant and operational biogas fermenters. The second pillar is biogas production from still active biogas sludge produced by the two main fermenters. The third is a biogas cleaning plant in which the produced biogas can be converted to natural gas quality. After the cleaning process, the gas can be fed into the natural gas distribution network. This creates the possibility of continuous biogas production throughout the year. The key of the concept is to keep the supply of raw materials needed for the biogas production at the lowest cost possible. The calculations show that the byproducts of sugar production (sugar beet pulp, molasses, beet tops, and pieces) and organic waste (weeds, other organic materials) can cover the total energy demand of sugar production. With plant-based byproducts coming from outside the sugar industry (bran, by-products of biodiesel production), the system becomes a net energy producer. The excess energy can be sold as biogas locally or can be fed into natural gas distribution network and even sold on international markets. Keywords: sugar factory, bio-energy, biogas, biogas cleaning, by-products