BIO ENERGY UNLOCKING THE BENEFITS OF WASTE


HRS is working with partners across the livestock supply and processing chain to help them reduce disposal costs, create value added co-products, and reclaim clean water from organic waste streams. Some of these companies are now selling high value fertiliser products, and the use of biogas for energy – for heat, electrical power or use as renewable natural gas– continues to increase globally. Matt Hale, international sales & marketing director, HRS Heat Exchangers, comments


A


s the world’s population passes eight billion, the need to conserve the earth’s finite resources and use them as efficiently as possible has never been greater. According to the World Bank, human waste generation will increase from 2.01 billion tonnes in 2016 to 3.40 billion tonnes in 20501


, with 40% of global municipal waste being food and green waste2. Other


sources of organic waste include crop residues, livestock manures and sewage. Livestock manure is a significant source of organic


waste materials. Although accurate figures are harder to come by, the Agricultural Research Service (ARS) of the U.S. Department of Agriculture (USDA) estimates that: ‘In the United States, as much as 1.3 billion tonnes of manure is produced by the 9.8 billion heads of livestock and poultry produced yearly.’3


As these figures show, livestock


manures and slurries account for as much organic waste material as other sources. This is significant as global greenhouse gas (GHG) emissions ‘from livestock supply chains are estimated at [more than] 7.1 gigatonnes CO2e per year.’4


TAKING CIRCULAR APPROACH It is widely accepted that the traditional model of a linear economy – where raw materials are mined or abstracted, refined, turned into goods, utilised, and then discarded at the end of their useful life – is not only wasteful, but unsustainable. In fact, over the course of human history such a linear model has been the exception, rather than the rule – becoming established as a concept around the same time as the first industrial revolution from the mid-18th century onwards. In a circular economy, bio-waste is not landfilled


and incinerated. Instead, it forms a resource for organic soil improvers, fertilisers, growing media component and bio-based products5


. The UN Environment Programme and Climate


and Clean Air Coalition has identified the treatment of organic wastes as being the most ‘immediate and cost-effective’ way to keep global warming below 2˚C, with anaerobic digestion identified as a key technology1


. Organic wastes


contain significant quantities of useful plant nutrients and organic matter, but if not treated properly can lead to environmental pollution and produce large quantities of greenhouse gases, such as methane and nitrous oxide. Therefore, intercepting these organic waste streams, and livestock manures in particular, and treating them appropriately provides a number of environmental benefits: • Prevents direct GHG emissions from the


decomposition of the wastes


• Prevents environmental contamination through incorrect disposal (e.g., phosphate and nitrate pollution of water courses)


• Aids odour management in sectors such as agriculture and sewage treatment • Has the potential to provide renewable energy via processes such as anaerobic digestion


• Provides renewable, organic fertiliser and reduces the pressure on finite resources such as potash


• Improves soil health through the use of renewable fertiliser with higher levels of organic carbon and organic matter


• Reduces indirect GHG emissions associated with the production of synthetic fertiliser.


TACKLING ORGANIC WASTE The first priority should be to prevent and minimise organic wastes and manures, but unavoidable organic waste is increasingly being intercepted and treated globally with technologies including anaerobic digestion and composting. HRS has worked with a number of partners around


the world to treat and valorise organic wastes from a range of sources, including sewage treatment, on-farm manures and slurries, and crop and food waste. For example, the company has installed practical manure and digestate management systems, the first of which was commissioned in


14 ENERGY & SUSTAINABILITY SOLUTIONS - Spring 2023


Spain, treating up to 12 tonnes of pig manure from a number of nearby farms every hour. The company has produced a wide range of systems for the pre-treatment, evaporation, pasteurisation and concentration of organic waste streams and the products of organic waste treatment, including manure, slurry, sludge and digestate. These systems are designed to reduce cost (for example by reducing the volume of material which needs to be treated, stored or transported) or increase value (by ensuring that biofertiliser is safe for crops and people) as well as being energy efficient and often improving the overall efficiency of the treatment process (for example, by reducing the need for external heat sources by recovering and utilising waste heat).


EVAPORATION AND CONCENTRATION SYSTEMS HRS treatment systems are particularly effective when used with liquid, or semi-liquid, waste streams, such as slurry, sludges or unseparated digestate. Evaporation is an efficient way of reducing the volume of effluents and wastes. HRS evaporation systems raise effluent, digestate or liquid waste to its boiling point (under vacuum) so that water is evaporated and then condensed, thereby obtaining a concentrated end product and condensate.


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