Waste management

Right now is the ideal time to improve how you handle waste material and doing so could deliver benefits, Sally Drury explains

EcoCombi: chipper/shredder reduces particle size for more effective heat treatment - image: Greenmech
EcoCombi: chipper/shredder reduces particle size for more effective heat treatment - image: Greenmech

There is a hierarchy to waste management - prevent, minimise, reduce, reuse, recycle, recover and, finally, after all other options have been considered, dispose. It is all about protecting the environment - water, soil and air - wildlife and public health.

Sometimes we are so busy developing landscapes, maintaining grounds, growing food, producing plants or preparing facilities that we forget to review things such as waste management. If you are just carrying on doing what you do because that is the way it has always been done, you could be missing out on some benefits. Worse, if what you are doing is wrong, you could be heading for trouble. Now, before the growing season really gets underway, is an excellent time to put some thought to the matter.

Not convinced? Think on this - anyone caught fly tipping risks a fine of up to £50,000 in a magistrates' court. A Crown Court can impose an unlimited fine and may send the guilty person to prison. Fly tipping is a serious offence. So is air pollution.

Burning

Some wastes can be burned in certain circumstances if you have the appropriate registered waste exemption. But, under the Clean Air Act, the burning of trade or commercial waste can attract a £20,000 fine if dark smoke is released. In addition, it is an offence under the Highways Act if smoke drifts across a highway and causes, or risks causing, an accident.

You may qualify for a D7 exemption to burn plant material and untreated wood in the open if you burn on the site where the waste is produced and you burn no more than 10 tonnes in 24 hours. If you produced the waste, it may be possible to burn it in a small appliance (D4 exemption) or incinerator (D6 exemption) with a capacity of less than 50kg per hour and total net-rated value of less than 0.4MW. Check with the local authority that you are not in a smoke-free zone. Fines of up to £50,000 can be incurred for illegal waste management under the Environmental Permitting Regulations.

Disposing of waste to landfill is expensive. Charges can range from £30 to £100 per tonne depending on the waste, and then there is the cost of fuel and time. Simply disposing to landfill can add significantly to business costs. Reducing, reusing or recovering materials can make good business and environmental sense.

Now start doing an audit of your waste so it can be managed properly and perhaps even bring some benefits to your operation. Start by listing the types of waste produced and where they come from. Most likely there will be cardboard boxes, polythene sacks, perhaps old polytunnel covers and broken glass, pesticide washings and containers, lubricating and hydraulic oils from machinery, dead parts and even whole machines, paper from the office, trimmings and prunings from shrubbery, weeds, etc. Then consider whether it can be prevented, minimised, reused, recycled or recovered, or whether it requires disposal.

Regularly review practices, considering the nature, quantity and costs of dealing with waste. Identify where waste can be avoided or consider how it can be reduced. Also identify where waste can be reused or recycled for a secondary purpose.

Think outside the box. Can spent oils be used for heating purposes if approval is sought? Could office paper waste be reused as animal bedding? Could green waste be dried for decorative purposes? Can you really use rhubarb leaves to kill aphids in the greenhouse? Shortlist potential improvements, including staff training, and make changes as opportunities arise.

Compost bays: rising temperatures kill weed seeds and the majority of pathogens - image: HW

Composting

When it comes to green waste, most material can be composted for use as landscape mulch, soil improver or potting medium. Composting is great. It not only solves a waste problem but also, made and used correctly, can improve soil structure and water-holding capacity, increase biological activity and supply nutrients - so potentially reducing the need for bagged fertiliser inputs.

Composting is controlled under Waste Management Licensing and regulated by the Environment Agency. Clearly commercial composters need a full waste management license but exemptions are available for smaller operators or for producing compost for your own use or on-site use and provided it is less than 1,000cu m of waste stored on-site at any one time.

Careful selection and handling of feedstock, plus management of the process, means a compost system can be beneficial and efficient without producing bad smells or leachate. But, at a time when plant health is so frequently in the news, measures should be taken to minimise risks of disease spread.

The Code of Practice for the Management of Agricultural & Horticultural Waste details measures that should be taken to minimise plant risks from residues and associated waste generated during the commercial handling of certain types of plant produce.

It is intended for growers and is voluntary but makes an interesting read for those from other sectors who handle green waste materials and suggests a risk assessment should be carried out in terms of the harmful organisms and likelihood of the spread of pathogens.

That risk assessment should include the source, type of plant material involved and the biology of the pests and diseases. Where risks are low, normal composting procedures may be sufficient, but heat treatment or alternative disposal may be necessary where there is a high risk of spreading disease - and remember it is best, where possible, to clean off the soil from bulbs, roots and weeds as they are lifted.

Composting is an aerobic and exothermic process - it is not sterilisation - but it can eradicate the majority of pathogens and pests. It also reduces the volume. In a properly constructed compost bay temperatures rise, usually to above 50 degsC and sometimes in excess of 70 degsC, as the high-energy compounds in the material are consumed. This phase kills weed seeds and most pathogens before dropping back to around 40 degsC as the rate of decomposition declines.

Recommendations

The European & Mediterranean Plant Protection Organisation (EPPO) recommends the entire mass should be exposed either to a temperature of at least 55 degsC for a continuous period of two weeks or 65 degsC for a continuous period of one week. Moisture content should be more than 50 per cent and there should be two turnings.

Importantly, temperature, along with moisture content, should be monitored and recorded daily from several zones of the mass. If moisture content is above 60 per cent, permeability to air will be reduced. That is when methane and unpleasant odours will be produced. Below 40 per cent also causes problems as organic compounds are less available to micro-organisms. Consider adding water if moisture content falls to 40 per cent or below.

Even with good composting techniques, some pathogens may survive. Club root (Plasmodiophora brassicae) is one pathogen known to be heat-tolerant and EPPO suggests processing such material at 74 degsC for four hours, 80 degsC for two hours or 90 degsC for an hour using wet heat. Should you be concerned about plant health status or require more information, contact your local Plant Health & Seed Inspectorate office. The Plant Health Helpline number is 01904 405138.

Turbo Shredder: big unit for green waste - image: Timberwolf

Shredding

In any compost system, for heat treatment to be effective, particle size should be small. Best results are obtained from chopped, well-mixed materials. It makes sense to shred green waste before composting, especially if it includes hedge trimmings, shrub prunings and other woody material. An efficient shredder is clearly an option.

There are plenty suitable for small and large-scale operations. For instance, small sites generating green waste throughout much of the year might consider one of the Eliet shredders from PSD Groundscare. For professional use, these range from the Eliet Major, capable of taking 55mm-diameter material, up to the SuperProf with 130mm diameter and available in self-propelled and towable formats.

PSD Groundscare also supplies TS Industrie chipper/shredder vegetation processors in the UK. More expensive, these units have larger capacities - 140-200mm. Larger still are the professional green-waste shredders from Timberwolf. These take material up to 426mm, have a throughput of up to three tonnes per hour and come in towable and tracked versions.

Greenmech's portfolio includes a range of chippers for tree surgeons but also offers a small gravity feed unit for public garden use and the EcoCombi combination chipper/shredder with 150mm capacity. Hardmet Landforce also offers a combination unit.

Alternatively, you could hire a machine when volumes make it economic or bring in a contractor. The Green Team in south-west London is one of many firms offering on-site green-waste recycling and shredding. Windsor Great Park hires in a huge tub grinder to smash its green waste and produces up to 10,000 tonnes of compost each year for use in the gardens and grounds. Now doesn't that make sense?

Phytobac uses bioremediation to degrade all contaminants - image: HW

Dealing with pesticides to avoid potentially serious pollution problems

Very small amounts of pesticide - even just the residue on the foil seal from a container - can cause serious pollution problems. Mixing, filling and washing operations must be carried out carefully and you should have an accident and emergency plan in place for spills and contamination.

It may be possible, depending on the product approval, to use washings to make a further batch of dilute pesticide or to apply washings to the treated or untreated crop. Triple rinse containers and use that liquid to dilute the spray.

Phytobac, a development supported by Bayer CropScience, is a simple and effective way to deal with dilute washings. The sealed, waterproof container is filled with a biomix of 70 per cent topsoil and 30 per cent straw, and allows contaminants that originate from filling, cleaning and washing of spray equipment to be retained and degraded by bioremediation.


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