Promoting a circular economy through sustainable wastewater and agricultural residue management

Sustainable waste management practices will be essential in order promote a circular economy. The over exploitation of natural resources required to achieve economic growth and development has negatively impacted the environment. Consequently, the idea of a circular economy, which offers new ways to create a more sustainable economic growth model, is very attractive. Membrane based separations are attractive as they are environmentally friendly. Here the use of membranes for water treatment and conversion of agricultural residues to value added products is discussed.

In this presentation the use of electrocoagulation as a feed pretreatment operation prior to membrane distillation will be described. Today highly impaired hydraulic fracturing flow back water is typically reinjected into a geologically isolated formation in the Earth’s crust. However, treating this highly impaired water for beneficial uses will promote a circular economy. The advantages of an integrated electrocoagulation, microfiltration and membrane distillation process for maximizing water recovery from hydraulic fracturing produced water will further highlight the potential for process intensification through integrated membrane based separation processes. 

Taken together all aspects of the agricultural industry contribute more than 25% of world greenhouse gas emissions. Agricultural residues represent an abundant source of fuels and chemical intermediates. Conversion of these residues to valuable chemical intermediates will not only extend the carbon cycle but also promote a circular economy. Here lignocellulosic biomass hydrolysis and dehydration has been conducted using a synthetic polymeric solid acid catalyst consisting of dual polymer chains grafted from the surface of a ceramic membrane. The acidic polymeric chain, poly(styrene sulfonic acid) (PSSA) catalyzes biomass hydrolysis as well as dehydration. A neighboring poly(vinyl imidazolium chloride) (PIL) chain helps solubilize lignocellulosic biomass and enhance the catalytic activity. Hydrolysis was conducted for crystalline cellulose and acid, base or steam pretreated corn stover samples in ionic liquids (IL) and mixtures of IL with water or γ-valerolactone (GVL). Near quantitative total reducing sugar (TRS) yields for cellulose hydrolysis as well as pretreated corn stover biomass were achieved at mild conditions and in less than 12 h. Other lignocellulosic biomass residues have also been tested as feed streams.  

Our novel, patented, polymeric solid acid catalysts are superior to cellulases as they can be operated at a higher temperature and at a much higher hydrolysis rate. These catalysts are stable and maintain high catalytic activity after repeated runs. Moreover, they can be easily regenerated and are environmentally friendly. These polymeric solid acid catalysts can be used not only for hydrolysis but also dehydration of cellulose leading to the production of 5-hydroxymethylfurfural (HMF) or levulinic acid.

Stories beyond the bin…

Statistics show that more than 38,000 tonnes per day of solid waste are generated in Malaysia, equivalent to nearly 14 million tonnes per year. These million tonnes of waste are reported to be either recycled, disposed of to the official landfill sites or some illegally dumped to the open dumpsites. It is a common scenario that most people wouldn’t care much on the waste after they have discarded it into the waste bin or segregated it for recycling, with a common mindset that they have done their part and thus what happens after the bin is not known and none of their business.    

This talk aims to provide some insight information on the stories beyond the bins, to illustrate the magnitude of the entire waste management problems that we are facing, particularly to also share some scenes that tell a thousand words about the real situation of waste management in Malaysia. How much waste actually are we generating? Isn’t waste making wealth? Are we doing enough? What are the key challenges and way forward of waste management in Malaysia? Are there any new wastes, new threats and new opportunities in the future of waste management? All these myths are expected to be uncovered in this talk.

Flue gas pyrolysis of organic & plastic waste

A fast pyrolysis system with a capacity of more than 1 kg/h using flue gas with organic and plastic wastes (OPW) is presented. If used in a commercial setting, the pyrolysis system diverts OPW away from landfills, reducing the associated greenhouse gas emissions. Most pyrolysis methods use pure nitrogen and are commonly performed at a lab scale setting, with capacities lower than <1 kg. The use of flue gas would reduce carbon emissions, while utilizing the latent heat present in the flue gas, which has average temperatures of 100 to 200degC.

The talk also includes operational experiences & limitations of using flue gas for pyrolysis, and the practical implications of the OPW’s composition. In addition, an innovative technology to modify the properties of the bio-oil via a non-thermal plasma reactor is presented. The talk also envisions other applications and opportunities as a result of the pyrolysis process.