Rocket® composter

Below are some of our most frequently asked questions, if you cannot find an answer to your question, please click here to email us your enquiry. 

» Why compost anyway? 

» What is the process of composting? 

» What should and should not be composted? 

» How does composting work? 

» Why does the Rocket® composter work so quickly? 

» What are the advantages of using the Rocket® composter? 

» How do we work with the Rocket® composter? 

» What are the running costs? 

» When is the composting process finished? 

» Why not put yard wastes in landfills? 



Why compost anyway?

Composting reduces the demand for landfill sites.
Apart from being offensive and unsightly, especially for people living nearby, landfill sites are expensive and have to be paid for either by industry or local council taxpayers. They produce unpleasant odours despite the greatest efforts of the managers to avoid them and can release greenhouse gases like methane. It is up to 25 times more potent, per ton, than CO2 in causing global warming.
Compost improves soil structure.
  Both water holding capacity and fertility are improved by adding humus to sandy soil while heavy clay soils gain improved structure and porosity.
Compost Helps Suppress Disease.
Various scientific studies show that the addition of helpful micro organisms present in the compost help plants to fight disease and some of the effects are quite dramatic. Work done at the University of California (1994-2000) highlighted the suppression of Brown Rot in Peaches, End Rot in Onions and Avocado Root Rot.
Compost reduces the need for pesticides.
Tests have shown up to 90% reduction in whitefly and complete elimination of aphids and red spider mite. They believe it is because the compost activates natural plant repellents.
Compost reduces the need for artificial fertilizers. 
By providing natural growth promotion, NPK fertilizers are less necessary and in agriculture, the run off of fertilizers into water courses are also reduced and nutrients from compost are less likely to leach out.
Compost reduces costs. 
The need to purchase soil improvers, compost and artificial fertilizers is reduced.
Compost suppresses weeds.
When used as a mulch, a layer of compost will help suppress weeds by reducing the amount of available light. Properly made compost will not contain weed seeds, but will also provide soil nutrients. Un-composted mulches e.g. woodchip or bark can reduce nitrogen levels in the soil and cause damage to plants, however compost used slightly before it is mature is extremely valuable for Vermiculture.
Compost helps to preserve Peat stocks. 
It is regularly reported that peat stocks are approaching extinction with current levels being down to 4%. Whatever the figure is, it is undoubtedly a finite resource and replacement products are needed. In this regard, a ?Gardening Which? report (Jan/Feb 2001) shows germination of Impatiens (Busy Lizzies) seeds in peat free or reduced peat compost is down to a minimum of 30% compared to minimum 54% in peat based material. Correctly made natural compost does not suffer this deficiency.
Compost enables organic horticulture.
Although there is a need to assure that no substances banned by the Soil Association are included in waste to be composted, properly made compost is the very basis of organic horti/agriculture.
Compost can eliminate digging. 
Compost used as mulch will be dragged into the soil by earthworms. This helps with soil aeration as well as with providing the required nutrients and in shrubby borders it can remove the need to dig.


 What is the process of composting?


Composting is a biological process that, in the absence of any manual intervention will happen of its own accord. Natural composting, or biological decomposition, began with the first plants on earth and has been going on ever since. As vegetation falls to the ground, it slowly decays, providing minerals and nutrients needed for plants, animals, and microorganisms. This compost would be consider a delight in any horticultural situation. The Rocket® composter, however, includes the production of high temperatures to destroy pathogens and weed seeds that natural decomposition does not destroy. 

Composting is as scientific as bread making and wine making. Leave flour, milk, water, salt, sugar, fat and yeast in unmeasured proportions in a bowl in the kitchen and although the bio-reaction will no doubt proceed, bread won?t be made and the result will hardly be a gastronomic delight! The same applies to composting and there are rules to follow if a quality product is the goal. 

There are 7 rules to produce quality compost rapidly. Expressed simply they are as follows: 
1   Take 'Green' waste. (A simple word for high nitrogen waste - grass, weeds, animal manure etc.)
2   Take 'Brown' waste (high carbon) - usually dry in nature, e.g. tree and shrub prunings, waste paper, woodchip, straw etc.
3   Shred and mix them.
4   Add micro-organisms for speedy action ? commercially grown materials are available.
5   Preserve and control the heat produced by the composting process.
6   Provide the correct water content and control it in its need to change during the process.
7   Control aeration.
To explain the rules further – 

Green waste: Is waste containing high nitrogen which is often green. Grass, vegetable waste, green leaves, weeds and some of their products of decomposition like manures of herbivorous animals like horses, cows, sheep etc. Although hardly green, they are high in nitrogen and also contain many micro-organisms responsible for decomposition of organic matter. This waste provides the heat necessary to raise temperatures to levels where the process is rapid and where pathogens like e-coli 157, weed seeds, slug eggs etc are destroyed. (Above 500c for 3 days) 

Brown Waste. The addition of ‘high carbon,’ both adds structure to the compost, and reduces nitrogen depletion in the finished product. These are materials – like prunings, paper, (use non glossy) wood chips, sawdust, straw, etc. 

Shredding and mixing. Reduction of particle size by any means possible brings the waste particles into close proximity and enables the micro-organisms to move from one particle to the next in search of food. The exposure of the internal parts of wood and other vegetable matter is extremely helpful. 

Add micro-organisms. The composting process is dependant on these in the form of fungi, protozoa, bacteria etc. in order to function properly. Many micro – organisms are present in the atmosphere and are really the ‘yeast of the process’ if you were to compare it to bread or wine making. However, for rapid results it would not be prudent to await the arrival of the appropriate micro-organisms. Certain accelerators can be purchased to contain specific micro-organisms to deal with the various organic materials which are predominant in the waste. These kick-start the process and facilitate rapid composting. 

Maintain and control heat. Decomposing organic matter will provide heat up to 900c given certain conditions, but this would be too high for most purposes. Normally, in domestic compost heaps under 8 cubic meters, and the heat produced will escape, and the mass will not reach the required 500c. Pathogens, weed seeds, slug eggs etc. will not be destroyed and the process of composting will take a long time. 

Provide the correct moisture content. Micro-organisms live in the film of liquid that surrounds the particles of solid waste that is their food. Too little and they starve and too much excludes the very necessary oxygen for aerobic fermentation- which would prevent the production of methane, a major greenhouse gas and which has a rank, very unpleasant odor. 

Provide aeration. Oxygen is essential in correct composting for the promulgation of the correct bacteria and allows the mass to reach the required temperature. It can be achieved by turning the heap or by air injection, but it must be carried out on a regular basis.
A study of horticultural and composting books and other publications shows conflicting advice on this subject. Not much is backed by scientific study. What is certain is that any organic matter will eventually decompose and therefore must be a candidate for composting. 

Using the Rocket® composter anything once alive, can be safely composted with very few exceptions. Meat or fish scraps which normally encourage rodents and flies can be included as it is a closed system which denies access to these pests. 

Avoid plants with serious diseases like honey fungus or sweet pea root rot, potato blight for etc. as small amounts may linger and affect future crops. Also omit grass and other plants that have been treated with hormonal weed killers etc. as even in small residual concentrations can cause damage. 

It is then that organic degradation is rapid and pathogens, fly larvae and weed seeds are destroyed. As thermophilic activity declines and temperature falls to 30-40° (Cooling stage) there is another series of organisms capable of growth at normal temperature. Finally, as the compost is left in a heap, preferably protected from too much rain (Maturation Stage) the nitrification stage proceeds and ammonia turns into nitrites and the nitrates. It is this final material that aids plant growth.

Unfortunately, in any batch process all the micro organisms – spores and all - are largely discarded and have to build up again in the next batch.

It was with all these considerations in mind and to find a way to overcome the various shortcomings of the present systems that the ’Rocket’ was devised.

 The Microbiology of Composting.

The biological degradation process of composting can be broadly described in terms of four stages of micro-organism activity, characterized by different temperature ranges.

At the beginning (Mesophilic stage) bugs operating at ambient temperature are required. These include fungi, bacteria and actinomycetes. At the same time acarines, millipedes and isopods will ingest the organic wastes. The soft tissue of the decaying plants supports growth of nematodes and enchytraieds.

These consumers then attract and become food for the next level of consumers – collembolans eat fungi, ptiliids feed on fungal spores. Nematodes ingest bacteria and protozoa and rotifers feed on bacteria. The energy liberated during this conversion causes a rise in temperature to between 45 and 70°c. At these higher temperatures (Thermophilic stage) a specialised flora of bacteria, fungi and actinomycetes take over. 


 Largely because it meets the 7 requirements of successful composting and importantly the other main reason is because normally in all batch processes the micro-organisms are all ejected as the compost container is emptied. However, because the Rocket® composter is a truly continuous process and the waste mass passes gently through the Rocket® composter, organisms are left behind to continue their work. 


» Speed of decomposition 
» Quality of finished compost 
» Freedom from weed seeds, slug eggs and pathogens 
» Cost effective 
» Little manual effort required 
» Conforms with current DEFRA rules for food processing 
» Virtually odor free 
» Access to rodents and flies is denied. 


 Once the waste material has been selected and if necessary, reduced in size, it is fed into the inlet of theRocket® composter. 

It is preferable in the Rocket® composter to start the composting process with a high water content, which produces almost anaerobic conditions and gets the process off to a quick start. The moisture level is controlled throughout the process so that the compost develops rapidly and then gradually dries out to emerge some 10-14 days later in a dry and friable condition – ready for use. 

Composting generates heat rapidly. The Rocket® composter has a heating element surrounding the first part of the reactor to kick-start the process and to ensure it can meet the required temperature for the needs of the particular process. The Rocket® composter is insulated to prevent heat loss. The waste material is then turned by a shaft, which is fitted with angled blades that lift it to aerate it. At the same time the shaft moves it forwards towards the exit of the equipment. 

The heating system has been designed to be variable to meet the different types of waste material requirements. High temperatures are achieved in the composting process by the normal reaction of decomposition during the thermophilic stage and are maintained for several days. During this stage, weed seeds, fly larva, slug and snail eggs are destroyed as well as most intestinal worms and pathogens that may be present, especially if animal manures are incorporated into the waste. 

These are minimal – normally only a few dollars per month depending on the Rocket® composter model. 


It depends on the final use for the compost i.e. a soil conditioner, as a mulch, or as a seed or potting compost. The Rocket® composter can be programmed so the compost emerges in about 9 days when it will be slightly under composted, where it is ideal for vermiculture as it has a residual food value for the worms. 

Or it can be process in 14 days to spread it in the ground as mulch. The lack of oxygen in this slightly under composted material helps to suppress weeds better. For seed and potting purposes it is preferable to leave it in a covered heap for at least 2-4 weeks to allow it to mature. For the very enthusiastic composters, it can be tested for maturity by placing it in a vacuum flask, taking the temperature and if tested again in a week’s time the temperature should not have risen. 

the Rocket® composter continues to use the generated heat to dry the compost to make it easy to handle. It can also be shredded further, or riddled at this stage if required. The type of waste material, ambient conditions and the required end product can all have an effect on time of completion. 

Since these materials are relatively clean and biodegradable, disposal in landfills may be unnecessary and wastes space. In addition, as yard wastes decompose in landfills, they generate methane gas and acidic leachate. Methane is a colorless, explosive greenhouse gas that is released as bacteria decompose organic materials in landfills. If methane is not controlled at a landfill, it can seep underground and into nearby buildings, where it has the potential to explode. Yard wastes also contribute acidity that can make other waste constituents more mobile and therefore more toxic. 




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