Biofuel

Abstract

The invention relates to a biofuel, particularly an advanced solid biofuel, comprising waste coffee grounds.

Description

FIELD OF THE INVENTION[0001]The invention relates to the use of biomass, in particular waste coffee grounds (“WCG”), including those produced by Instant Coffee Factories (“ICFs”) as a biofuel, particularly as an advanced sold biofuel. The biofuel may be provided, for example, as a WCG-derived biomass pellet (“pellet”) and a WCG-derived biomass briquette (“briquette”). The invention provides the biofuel itself, as well as methods and apparatus for producing it.BACKGROUND TO THE INVENTION[0002]WCG are a type of biomass. Biomass is organic material produced through the reactions between carbon dioxide in the atmosphere, water and chlorophyll, via photosynthesis, to produce carbohydrates. During photosynthesis, agricultural crops absorb solar energy that is stored in the form of chemical energy in the bonds of the biomass components. The stored energy in these bonds can be released via combustion of the biomass, and by digestion of the plant for the nutritional content contained within ...

AI Technical Summary

Benefits of technology

The invention provides a combustible biofuel composition that includes WCG (spent coffee grounds) and a binding agent. The composition can be made into pellets or briquettes for use in biomass boiler systems. The composition should contain at least 45% WCG and may contain more than 50% WCG. The composition should also contain a calorific material (a combustible filler) that helps control emissions and maximize calorific output. The composition should also have a particle size of less than 2 mm for durability. The binding agent can be a surfactant, emulsifier, or gelling agent, and can improve the ability of the composition to be made into pellets or briquettes. The composition should have a hydrophilic-lipophilic balance of binding agents between 7 and 15. The amount of binding agent used in the composition should be between 0.5% and 10%.

Problems solved by technology

Previously it had been understood that using WCG to produce pellets or briquettes for burning in biomass boilers or in stoves or the like would not be possible, due to the high oil content of the WCG.

The prior art on the processes used for making pellets and briquettes indicates that it is very difficult to form pellets or briquettes from compositions containing more than about 8% oil or fat.

Such logs would not be suitable for use in a biomass boiler, as the amount of ash that would be produced by burning the logs would rapidly fill the boiler.

Problems with ashing may also be seen if the logs are used with stoves or in fireplaces, the ash having to be cleared regularly.

Those IWCG are difficult to store and hard to transport for disposal.

To dry the IWCG requires significant energy input, which may not be desirable from a cost point of view.

Further, storing dry IWCG poses some risks since the IWCG have a tendency to self-ignite.

Directly incinerating IWCG is an expensive and inefficient activity due to a high moisture content and the requirement for flawless, continuous 24 / 7 / 365 processing.

Additionally the machinery sometimes used for incineration of IWCG—fluidised-bed boilers—are very expensive to build, install and very inefficient, expensive and complex operate; indeed, they often require teams of highly experienced engineers and operators.

Due to large-scale, outdated, monolithic engineering, regional waste management schemes and inconsistent local waste disposal infrastructure, no single solution for treating the IWCG produced exists that can be applied across this potential 40-fold shift in scale.

This results in IWCG being disposed of off-site in most scenarios, costing both the ICF and the environment as this waste usually gets sent to landfill or incinerators.

IWCG do not perform well in anaerobic digestion due to low biomethane potential, low levels of protein, gritty nature and particle size.

ICFs require significant amounts of energy (heat, steam and power) to run.

As mentioned on previously it had been understood that using IWCG to produce a solid biofuel would not be possible, due to the high oil content of the IWCG (IWCG and WCG compositions typically contain between 20 and 25% oil and fat) and the lack of fibre in the material.

The prior art on the processes used for making solid biofuels, particularly from biomass, indicates that it is very difficult to form solid biofuels from compositions containing more than about 8% oil or fat.

Further, IWCG comprise particles of a fairly uniform, large size and high elasticity, making it even more difficult to produce a solid biofuel with high mechanical durability.

The large particle size increases the likelihood of fissures.

Further, the extent of processing applied during the production of instant coffee means oils usually held at cellular level may be released, and starches contained in the grounds may have been gelatinised, making bonding the particles together even more difficult.

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