Enzymatic Hydrolysis

 

Enzymatic hydrolysis

Introduction:

The central idea of enzymatic hydrolysis is to use a smart cocktail of enzymes for the conversion of complex biomass/waste streams into energy and biorefinery feedstocks. Enzymes are nature’s own (bio)catalysts. Being catalysts means that they are able to lower the energy needed to let a specific reaction happen, without changing their own structure during catalysis. Enzymes are highly specific (one enzyme for one reaction).


Enzymes are natural bio-catalysts.

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Potential:

Enzymatic processes can convert of complex lignocelluloses from biowaste streams into monomers that can be used as ‘building blocks’ in biorefinery applications and energy applications.

Aim:

The objective of the research is to develop a bio-economy in biorefining & bioenergy by processing complex biowaste streams (containing lignocellulose) into monomers that can be used as ‘building blocks’ in biorefinery applications.

Difference to BAU technology/approach:

Most of the wastes evaluated for enzymatic bioconversion into energy and biorefinery feedstocks present current and/or future waste management problems for industry, and the current re-use practices are frequently of low value or not developed.
For example:

  • Recycled paper waste is exported from Ireland (not utilised in Europe)
  • Spent grains and wheys are given to farmers for use in animal production (more is produced than can be used in this context, which leaves surplus waste)
  • Food and OFMSWs are low-grade wastes and are largely under-utilized; some composting is carried out, but due to contaminants land-spreading of the products is limited.
  • While some agri wastes are re-used (e.g. cereal straw and poultry litter in mushroom production), the greater bulk of agri-residues is not re-used for higher value bio-refining purposes.

Enzymatic bioconversion is an enabling technology that reduces the organic biopolymers (the highest proportion being sugar-rich) to simple building blocks (e.g. single sugars), which can be utilized and transformed through fermentation to produce higher value products. The enabling enzyme technology can be described as a green technology as the enzymes/enzyme systems are sourced from environmentally benign microbes (mainly fungi). The manner in which the enzymes are used (i.e. approach to bioconversion) is also environmentally friendly as the enzymes are cell-free systems and consequently, their application does not pose a risk in terms of transfer of microbes to the environment.

Input stream requirements:

The technology of enzymatic treatment is applicable to different types of organic waste streams such as mixed wastes, agri-wastes (straw-stover), forestry wastes, marine wastes, food wastes and paper and cardborad wastes. 

Available quantity:

Very large – broad scope

Drivers for treating this stream:

There is a recognised need among policy makers that Europe needs to increase waste re-use and move closer to a ‘zero’ waste culture. At present the vast majority of recovered waste paper from the NW region of Europe is exported. In Ireland the largest proportion of waste paper is exported to countries like China. This material represents a potentially valuable raw material for a range of higher value consumer products, including biochemical, bioplastics and platform biofuel feedstocks. In addition, the agri-sector in Ireland and the NW region of Europe is facing a predicted expansion due to increased global demand for food and dairy products, and in the case of Ireland, changes and expansion in the agri sector due to reform of the EU Common Agricultural Policy. Agri-residues volumes will consequently increase, yet these residues represent valuable and sustainable resources for production of biofuels, platform biochemicals and chemicals, bioplastics, biofuels and recovery of nutrients (e.g. N and P). Furthermore, some wastestreams can be combined in co-treatment formats (e.g. using anaerobic digestion) with waste water streams, to recover water, which is also a very valuable resource. 

Potential environmental risks related to this waste stream:

The organics-rich nature of the wastes targeted leads to their biodeterioration in the natural environment. However, this process frequently takes a long time and can result in downstream pollution and eutrophication of water systems. Furthermore, specific waste streams (e.g. the organic fraction of municipal solid waste; OFMSW) may be contaminated with inorganics, which can pose issues in relation to environmental toxicity. 

Economic/technical barriers to collect this stream:

In many countries there is no integrated approach to collection of the waste streams. Collection is fragmented and dispersed. 

Output stream:

Organic outputs are obtained, such as sugar-rich feedstocks for production of biochemicals,  bioplastics and biofuels (e.g. biogas, bio-butanol & bioethanol). Bio-oils from oil-rich wastes.  When starting from specific food waste streams: protein and carbohydrate-derived nutraceuticals.

Different output streams and applications


Processed paper waste

 

Potential uses of this output stream:

Biogas and bioethanol can be used as bio-fuels. Monomers can be used in biorefinery applications, for instance to produce bioplastics and high value platform biochemical such as lactic acid and succinic acid. Nutraceuticals are food additives.

Biofuels

 

 

Potential environmental risks/benefits related to this output stream:

Transformation of the target organics-rich wastes to higher value feedstocks for commodity products, platform biochemicals and/or nutraceuticals has the potential to transform the wastes to resources, as well as reducing the impact of effluents/leachates from the wastes on the environment and water streams.

Economic barriers/drivers for market introduction of this output stream:

Economic barriers: No national and few integrated European approaches or legislative drivers to incentivise waste collection, reuse and transformation by industry and industrial uptake of output streams. No scale-up facility to test and optimize start-to-end waste to resource process development for industry. 

Technical barriers for market introduction of this output stream:

Financial support for industry to adopt and develop new technologies for production of output streams, as well as the uptake and market integration of outputs.

Legislative barriers for market introduction of this output stream:

There are some barriers around the current recycling practices for waste paper, as the bulk of this waste is shipped overseas rather than used as a resource for biorefining and bioenergy products. Depending on the paper source, there may be barriers (e.g. sanitary and health issues) relating to its use in products destined for human and/or animal purposes.

Pilot description:

The pilot will focus on the conversion of mixed wastes, agri-wastes and foodwastes with mesophilic, thermophilic or psychrophilic enzymes into bioenergy and bioplastics. Specific food waste streams can be converted into nutraceuticals.

Installation:


Enzyme fermentation facility

Capacity:

Small pilot scale – 100 L Enzyme production (150 L bioreactor)

Scale of the equipment:

Small pilot scale

Main technological barriers for market introduction:

The need to demonstrate, prove and validate the technology at scale for specific industry sectors.

Main economic barriers/drivers for market introduction:

Need to reduce cost of enzymes in bioconversion applications and to demonstrate at scale, the value-added potential of this alternative, environmentally-benign approach to support higher value re-use applications for lower value biowastes, e.g. waste paper and whey.

Research steps:

Reducing cost of enzymes in bioconversion applications by:

  • Low-cost enzyme production
  • Increased enzyme performance in conversion at lower dosages
  • Increasing enzyme half-life and ‘recyclability’

Scale-up testing with integrated modules at pilot plant scale in an integrated format.

  • Large-scale production of enzymes, followed by sequential enzyme-mediated pretreatment of organic-rich waste biomass at a large pilot scale facility (e.g. BioBase)
  • Downstream processing by fermentation (VITO, TCBB) and/or anaerobic digestion (TCBB) to produce and/or recover high value added platform chemicals, biochemicals (e.g. succinic acid), bioplastics and/or biofuels (e.g. biobutanol, biogas)
  • Process validation, detailed cost analysis and LCA – BioBase and ReNEW
Economic steps:

Reducing costs related to the use of enzymes in bioconversion applications (see ‘Research steps’) and process integration and optimization with downstream biological conversion systems (e.g. fermentations). Tax reform and subsidies for an initial period would greatly incentivise industry uptake and development of bioconversion technologies in which the enzyme technology is used as an initial, enabling bioconversion technology. The economic development of the technology and outputs are dependent on support to develop a central pilot test-bed facility for industry.

Other:

At present the potential of the technology for the efficient reduction (bioconversion) of biopolymers in biowastes to their simple building blocks has been established through lab to small pilot scale application studies. Aspects of the bioconversion need to be refined to:

  • Reduce processing times and costs
  • Decrease costs associated with the enzymes in the overall processing costs
  • Develop robust enzymes/enzyme systems to address inter-batch and inter-region variability of wastes
  • Optimize the recovery of valuable platform chemicals, biochemical and biopolymers from the feedstocks
Contact details:
Organisation: TCBB at UL/NUI Galway

Department: School of Natural Sciences

Leading researcher: Maria Tuohy & Bart Bonsall

Phone number: +353 91 492439

E-mail: maria.tuohy@nuigalway.ie & bart.bonsall@ccbb.ie

 

Documentation:

Presentation: Enzyme production & enzymatic conversion lignocellulosic feedstocks, Dr. Maria Tuohy, TCBB & NUI Galway, RENEW Technology Foresight Conference 24/04/2013