IE62649B1 - A natural and renewable organic compost/fertilizer - Google Patents

Abstract

A process is described for preparing a compost comprising selecting the uncontaminated residues or by-products of the food or health care products industries, admixing the selected by-products, forming the mixture into a heap and permitting aerobic fermentation of the mixture to occur. Also described are organic composts or fertilizers.

Description

The invention relates to a process for the production of an organic compost/fertilizer and an organic compost/fertilizer.

As used herein the term compost means general composts, plant growth media, soil conditioners, fertilizers and organic fertilizers.

Composts are obtained from the controlled degradation of organic matter such as plants or vegetables. These composts are used as fertilizers due to their recognised soil conditioning and enriching properties.

Composting consists of mixing carbonaceous wastes, such as leaves, straw, paper, husks etc. with nitrogenous wastes, such as food waste, grass clippings, animal manures etc. and permitting microbial breakdown in aerobic conditions. In conventional composting, the most important factor governing the process is the carbon/nitrogen ratio. A C/N ratio of 30/1 is considered optimum; above this, a longer composting time is required, and, below this, nitrogen is lost in the form of ammonia gas.

Normal composting losses are in the form of carbon dioxide and water with losses of up to 70% of the total composting mass. This carbon loss reduces the C/N ratio so that mature composts have C/N ratios of between 10/1 and 15/1 which is close to optimum for the soil.

Composting also has a sterilisation effect on the raw materials which is a function of time and temperature. However, composts are frequently prepared without regard to the condition of the raw materials and the presence of artificial additives therein e.g. pesticides, the presence of undesirable or deleterious organisms such as coliforms and the presence of mineral imbalances.

Temperatures are not sufficient to inactivate many of the modern day drugs and pesticides that may accompany the raw materials. Also, many modern day composts can carry animal and human pathogens (e.g. Salmonella) depending on raw material sources and the composting conditions.

Due to the lack of and untenability of quality assurance of the raw materials, the resulting compost cannot be guaranteed safe, natural and 'organic' i.e. produced without artificial fertilizers or pesticides.

It is an object of this invention to overcome the problem of contaminated composts, by providing a completely natural, renewable, safe and organic compost which can be used directly or diluted with other substances to provide a general compost, plant growing medium, soil conditioner or fertilizer. it is a further objective of this invention to consistently provide for a range of soil and plant care products which are nutrient rich and release their available nutrients to soils and plants at varying rates without the use of artificial additives, ingredients or fertilisers.

It is a further object to provide a process for producing a compost in which the loss of ammonia (an environmental contaminant) is reduced and which has a greatly increased compost yield. Another object of the invention is to provide a compost in which the available nitrate and ammonia levels are so low that the compost can be used as a plant substrate without further dilution.

According to the present invention there is provided an organic compost comprised of the uncontaminated residues or by-products of an established safe food, health or other production process. It is necessary that the raw material has passed the same quality assurance procedures as the ingredients that go to make the food, health or other product, or the products themselves.

In one embodiment, the invention provides for the addition of further , raw materials (additives). However, these additives are required to be natural, and safe to plants and animals. These natural additives may help facilitate the degradation of the raw materials (composting) by a natural or specially selected inoculum of a culture of microorganisms. In addition, they may enhance the soil conditioning characteristics of the compost.

The invention provides a range of composted soil and plant care products which are natural, safe and organic and uncontaminated having passed the same quality control procedures as the food/drink or health process from which the ingredients are derived and have a plant nutrient (specifically nitrogen) availability/ status which is a function of the composting and pre-composting processes (specifically heat treatment) of their preparation.

According to another aspect of the invention there is provided a process for preparing a compost comprising selecting the uncontaminated residues or by-products of the food or health care or other products industries, mixing the by-products, forming the mixture into a heap and permitting aerobic fermentation of the compost to occur.

Preferably at least some of the by-products having been subjected to a heat treatment step in which the by-products are heated to at least 60°C for at least 30 seconds, the heat treatment either being integral to or separate from the food or health care or other product production process. If it is desired to produce a compost in which there is no available nitrogen, then all of the components of the compost should be heat treated. However, if it is desired to have 100% available nitrogen, then none of the ingredients should be heat treated. Composts with varying degrees of available nitrogen can be produced by varying the amount of heat treated components selected for composting. The nutrients in the compost are variously available in so far as they are bound in the inter- and intra-molecular structure of the heat treated residue.

Preferably the by-products have been heated to at least 150°C. The heat treatment should be to a temperature sufficient to cause the proteinaceous materials to be linked to the residues (usually the £ fibrous portion) such that this linkage retains the nitrogen in a non-soluble form throughout the subsequent composting and provides a - 5 slowly available nitrogen source when used as part of a soil amendment or growing medium.

The composting process is controlled and monitored by maintaining the internal temperature of the heap in the range 45°C to o0°C, and periodically re-mixing the ingredients. The actual temperatures reached and the number of mixings of the ingredients required are a * function of the composition of the microbial culture inoculum, and the nature and amount of the raw materials. The development of a dark colour at the centre of the compost heap may be used as a guide to the adequacy of aeration and temperature development throughout the heap. Effluent from the heap is recycled onto the heap to retain nutrient and moisture contents of the compost/ferti1izer.

Another aspect of the invention is the incorporation of an organic structural component such as organicallv/ grown cereal straw into the compost, preferably in the chopped or shredded condition, at the appropriate stage through the composting process so as to improve the structure and porosity of the final product on the one hand while optimising the carbon/nitrogen ratio on the other. This does not interfere with the mixing of the compost with any structural component after the composting if this is thought desirable.

Clean uncontaminated bark is another example of a material that may be incorporated into the compost to serve a similar function as the shredded straw.

The process of this invention makes possible the composting of organic materials with a carbon : nitrogen ratio approaching 10:1 - the ideal for plant growing media - without significant loss of ammonia and other nitrogenous materials for the composting mass. It has not previously been possible to effect this control by simple, practical and natural treatments. Most authorities on composting claim a requirement for carbon/nitrogen ratios of 25:1 as a minimimum if substantial ammonia (and thus nitrogen) losses are to be avoided.

Composting can also be achieved by forced aeration of the heap or by using a reaction vessel which allows agitation of the composting mass. - 6 Natural additives such as limestone and gypsum are not essential to the process, however, in a particularly preferred embodiment of the invention they may be used to optimize composting conditions.

A wide range of raw materials may be used from the food processing industry, although this source should not be considered to be an exclusive one. These include by-products, residues and extracts such as: brewers grains, brewers dark grains and pale grains, roast house and malt house dusts, traub and yeast residues, dried brewers grains, hops residue, distillers grain cake, draff, pot ale, pot ale syrup, grains syrup, distillers dried grains, distillers dried grains with solubles; sugar refining by-products of both beet and sugar cane origin; seed and cereal coats and polishings including wheat, oats, barley, rice, maize and sorghums, cereal extraction residues; residues from coffee extenders or cereal drink manufacturing; starch and sugar extraction residues; other alcohol fermentation residues such as corn distillers residues; other fermentation industry residues such as citric acid production residues; residues of microbial amino-acid production; secondary food processing and refining wastes; or by-products from health products industries, which have had intimate contact with the food or health product produced and which have subsequently not been undesirably concentrated or contaminated.

Raw materials from the health products industries may include the by-products of herbal medicine, herbal extracts, microbial cultures, probiotic manufacture and natural pharmaceutical manufacture by-products.

Peat products and vermiculites are examples of materials which may be added to the compost mix to aid the soil conditioning characteristics of the compost produced e.g. porosity and aeration.

Materials or additives to the above are permitted where they facilitate the degradation of raw materials, e.g., natural microbial inoculants, or improve the physical or chemical balance such as straws, bark or other 1ignocellulose. In all cases, these additives must be natural £ and safe to plants and animals and permitted by the relevant local ORGANIC Symbol Standards Authority.

RAW MATERIAL PREPARATION The raw materials are blended before composting depending on the composted product required. Where an organic fertilizer is required containing readily available nutrient sources, then a non-heat treated high nitrogen material (e.g. Pale Brewery Grains) is mixed with a high carbon material (e.g., Cereal Straw).

Where a slow release fertilizer source is required as a mulch, soil conditioner or substrate for a growing medium, a heat treated high nitrogen material (e.g., Black Brewers Grains) is mixed with the high carbon material (e.g., Cereal Straw).

Where a Growing Media is required with a mix of available and slow release nitrogen sources, then a mixture of Pale and Black Brewers Grains is blended with the straw before composting.

In all cases, the moisture content is brought within the range of about 50% to 72% (w/w dry matter) by blending wet and dry materials and adding water where required. Comminution of longer particles to 5mm to 75mm range will help optimise the subsequent composting.

COMPOSTING The composting can be carried out using natural or forced aeration. The process is controlled by optimising the internal temperature in the range 45°C to 55°C. This is effected by controlling the supply of air through mixing or forced aeration.

A high temperature peak of 50°C of 12 hours will effect a kill of potential pathogens. Maintaining active fermentation for 2-3 weeks or until the temperature begins to drop off naturally will ensure adequate composting before a minimum six weeks maturation period when the compost is stored to maturity in a pile which optimises the surface area/volume ratio. Measurement of pH throughout the composting will give an indication of the ammonia being released from the composting mass. A peak of pH 7.0 will confirm minimal release of ammonia from r. the compost. „ 8 The invention is further described in the following examples. The examples are given by way of illustration only and are not intended to limit the scope of the invention with respect to composting materials and conditions.

Example 1.

This example describes the production of any organic fertiliser using Brewers pale Grains and permitted additives of Organic Symbol Standard: The following ingredients are mixed throughly: 600 kg of Pale Brewers Grains 120 g of a proprietary microbial composting culture in a suitable 15 organic carrier kg of limestone flour 15 kg of Gypsum flour (dust).

The mixture is mixed into a cone on a smooth floor and after 5 days or 20 when the surface temperature reaches 60°C, is further mixed. Mixing is continued on alternate days (or as frequently as is required to keep the peak temperature below 65°C) until the average heap temperature is in the range 45°C to 55° for four days.

Example 1 - Growing Tests: Pot tests with grass grown in soil supplement with composted fermentation grains as an organic fertiliser.

A series of composts so manufactured in 1988 were tested as to their effect on grass growth over the following two growing seasons.

Summary Report - May 1991 - (2 years growing trial) Soil was mixed with the composts at ratios of 15:1, 7:1 and 3:1 v/v to approximate field treatments of 40 tonnes, 80 tonnes and 160 tonnes per hectare. These were filled into 18cm pots.

Pots were sown with Ryegrass seeds (Lolium perenne), October 12, 1988. f.

After germination they were overwintered in a cold greenhouse and put outside during the 1989 growing season. Four harvests were taken between May and November in year 1 and 3 harvests in year 2.

Pots remained outside with no treatment except for regular watering. 5 TABLE 1 TOTAL FRESH GRASS GROWTH Compost l.D. (Source) Control Soil: 15:1 Compost Mix 7:1 v/v 3:1 10 — — — — — PBG05 (Brewers Grains) Year 1 117 243 348 530 Year 2 85 185 255 360 15 DGSP (Distillers Grains) Year 1 117 230 315 400 Year 2 85 150 245 310 20 MIX600 (Mixed Grains) Year 1 117 211 361 414 Year 2 85 150 215 275 25 CPI (Various Composting Systems) Year 1 117 259 280 473 Year 2 85 195 255 310 ------------------—, — * Data are the sum of the three replicates and expressed in grams < 30 fresh grass. Control yields were less than treated at all harvests. Tests we discontinued in Spring of year 3 when all pots had become badly leached and regrowth was equally poor in all.

This grass growing trial illustrates that composts manufactured by the methods of this invention from raw materials that have not been heat treated ~ in this example pale brewers grains, distillers grains - 10 and mixtures thereof - will boost grass growth up to 500% in the first year and up to 300% in the second year.

Example 2 : COMPOSTING OF BLACK AND PALE GRAINS WITH RAPE STRAW This example illustrates the differences in the composting process, the analytical parameters and the yields of composts made from Black Brewers Grains (heat treated) and Pale Brewers Grains (no heat treatment).

In this experiment both black and pale grains were composted with rape straw and bark in the ratio 75:15:10 on a dry weight basis. The mixes are outlined in Table 2.

TABLE 2 Materials used in second composting experiment (kg) Dry Wt. %DM Fresh Spent grains 80 25 320 20 Straw 16 83 19 Bark 10.7 60 18 These materials were mixed on October 25 and composted in the same boxes as the previous experiment and the same frequency of turning applied. The temperature in both mixes rose quickly above 50°C. After 10 days, the temperature in the black grain mix started to decline whereas temperature in the pale grain mix remained high until day 26 when it began a sharp decline. Composting was complete after 30 days. Analysis of the mixes during the composting period are shown in Table 3. “11Table 3 : Analysis of the spent brewery grains/rape straw mix during composting.

Date Black grains Pale grains pH %N C/N %nh3 %Ash %DM PH %N C/N %nh3 %Ash %DM Oct 25 4.8 3.5 13.8 0.00 3.5 31 8.0 3.1 15.6 0.36 4.0 33 Oct 30 6.0 3.6 13.5 0.00 3.5 30 7.1 3.3 14.7 0.42 3.9 30 Nov 5 5.9 3.9 12.5 0.01 3.9 31 8.2 3.0 15.8 0.46 5.0 41 Nov 12 6.1 3.7 12.9 0.01 4.0 32 7.7 3.7 12.6 0.36 5.9 40 Nov 19 7.7 4.4 10.5 0.45 7.2 50 The analysis of the black grain mix is quite stable throughout the period, indicating a much lower level of microbiological activity despite the high temperatures reached early in the composting. Little or no ammonia was measured and there was no characteristic smell from this mix at any stage. From the point of view of those working on the turning operations, this was a distinct advantage. In the pale mix the pH and the ammonia level had already risen sharply by the first sampling date. There was the same increase in the ash content and reduction in moisture content as in the first experiment.

The dry matter yields (Table 4) differed sharply between the two mixes. The lack of activity in the black grain mix, as indicated by the analyses, is reflected in a dry matter yield of 78%. The pale grain mix, by contrast gave a yield of 35%, in line with the previous experiment.

Table 4 : Dry matter loss during composting of grain/rape straw mixes BLACK grains Pale grains F.Wt %DM D.Wt F.Wt %DM D.Wt Before 107 107 After 258 31 83 59 55 38 Dry matter yield 78% 35% Example 3 PHOTOTOXICITY TESTING The example illustrates that heat treated brewers grains composts (Black Grains in text) are not toxic to seeds even when seeds are placed in the pure extracts. This result is in contrast to the response with the non-heat treated compost ingredients as illustrated below.

Decaying plant remains can be toxic to living plants and one concern about incompletely composted material is phv'totoxicity. To detect this, a germination test is used, with a quick germinating species such as cress.

An extract of the black and the pale grain mix was prepared as follows. A 250 ml beaker was filled with the material. Water was added until the surface of the material was glistening. The mix was left for one hour and then the solution was extracted by straining the material in muslin. A filter paper was placed in a 9 cm diameter petri dish. Three ml of the extract or a dilution thereof was pipetted onto the paper. Ten seed of cabbage or cress were placed on the moist filter paper. The dish was covered and placed in an incubator at 25°C. The germination was recorded after two days. Each treatment was replicated three times.

The results of one such test are shown in Table 5. In these tests, t. cabbage germinated more quickly and successfully than did cress. This may be due to the source of cress seed. The black grain compost did - 13 not affect germination even when the pure extract was used. Pure extract from the pale grain mix almost completely inhibited germination. As the concentration of the extract was reduced to 25% this effect was reduced and eliminated.

Table 5 : Effect of extract from compost on germination (as a percentage) Treatment Cabbage Cress Control 87 6 Black qrain + straw Pure extract 77 17 50% 87 6 25% 77 20 Pale qrain + straw Pure extract 7 0 50% 50 7 25% 87 23 Example 4 This example illustrates that composts made according to the specification of this invention in commercial quantities and conditions, are completely free of any pesticide contamination.

Black Brewers Grains (heat treated), Pale Brewers Grains, Rape Straw (2 different farm sources), Wheat straw, Bark Chippings (matured), and Dolomite limestone flour were the ingredients used in a series of four test batches of composts manufactured according to the specifications of this invention. - 14 COMPOSITION OF THE MIXES Tonnes Cl Black Brewers Grains Rape Straw (chopped) Dolomite 52.560 2.730 0.150 55.440 C2 Black Brewers Grains 50.720 Wheat Straw (chopped) 2.736 Dolomite 0.100 — 53.556 C3 Black Brewers Grains 25.500 Pale Brewers Grains 10.040 Bark Chipping 3.300 Rape Straw (chopped) 3.652 42.492 C4 Black Brewers Grains 77.440 Rape Straw (chopped) 7.014 84.454 The Brewers by-products were delivered directly from the Brewery, still hot, and essentially sterile.

Ranges Temperature of Brewers Grains 31°C - 57°C Dry Matter 21% - 26% Density 700 - 775g/l pH 4.4 - 5.3 The straws were chopped using a Kidd 7-16 Bale Chopper with a short chop kit. The Spruce bark been screened and stacked outside for 3 - 15 months before delivery. The Brewers Grains, Straw and Bark (for C3) were mixed on a concrete pad using a mechanical shovel before stacking in windrows 2.5 metres wide and 1.5 metres high. During composting, the windrows were mixed on average every three days for 3 weeks.

The Dolomite was added to Batches Cl and C2 to increase pH one unit after rainfall and caused an acidic fermentation — this prolonged the active composting period in these cases.

After 3-4 week mixing sequence or until the temperature began to reduce in the windrows (indicating a slowing down in active composting) composts were heaped up under cover and left to mature.

Regular sampling and analysis were carried out throughout the composting period.

Analyses of Nitrogen in Composts — sampled at 21 davs Total Available (ppm) % Total N(NO3) Cl 4.0 212 C2 3.8 253 C3 4.0 1,800 2 C4 3.9 800 1 Note that all batches had similar levels of total nitrogen at 21 days of composting. However, only one batch [(C3) made from non-heat treated Pale Brewers Grains] had significant levels of available nitrogen. The low level of available nitrogen in the other batches was characteristic right through the composting period. For example, Batch Cl after six months maturing, had only 11 ppm of NO, nitrogen and 275 ppm of total available nitrogen. These values are 10 to 50 times less than normally expected from similar conventional composts with 4.0% total nitrogen. - 15 With respect to possible contaminants in the composts, each of the above composts, between 5 and 12 weeks of maturity, were screened for 75 possible pesticide residues. Results indicated that none of the pesticide residues were detected in any of the composts produced by the processes specified in this invention.

Example 4 illustrates that composts produced by the processes of this invention can have predefined available nitrogen levels (some levels can be 50 times those of others) and are completely free of pesticide contaminants.

The following are results of of pesticide residues.

Sample No. Commodity compost samples analysed for the presence Ref.

Residue Detected 17286 Compost Cl 17287 II C2 17788 II C3 17289 II C4 None Detected II Example 5 GROWTH OF TOMATO SEEDLINGS IN A SPENT BREWERY GRAIN/PEAT SUBSTRATE This example illustrates that composts manufactured from non-heat treated materials (MIX 600 in this example) by the processes of this invention are effective fertiliser sources in growing media without the addition of any other nutrients.

This experiment was carried out to study whether composted grains could serve as a nutrient source for plants in peat compost without the addition of any other fertilisers. The grains used had been composted some time before (M. Clancy, Mix 600) and so had gone through a composting and then an ageing process. The analysis of the material was as follows (%DM); N:4.5, Psi.3, KsO.5, Mgs0.5. - 17 ~ The bulk density of the peat, medium grade baled moss peat, and the composted grains were measured. Amounts of grain and peat were weighed and mixed so that six substrates with proportions of grain of 5, 10, , 20, 25 and 30% by volume were prepared. The six mixes were then divided into two and to one half of each mix, dried blood was added to 3 provide 100 mg of N per m of substrate.

Each of the twelve treatments was then filled into 10 plastic pots, 11 cm diameter and a tomato seedling was pricked out into each pot. The pots were then laid out in randomised order on a floodbench in a glasshouse. The pots were irrigated from below once per day. The results were analysed as a 6 x 2 random factorial with 10 replications. In addition, there was an isolated control treatment of peat with PG fertiliser (a dutch design standard chemical mix for addition to substrates for container plants which is in widespread use in the trade) added at 1.5 kg/m .

The seedlings were pricked out on August 3 and were harvested on August 29. Plant growth was very uniform in all treatments during the early part of the growth period. The fresh weights of the plants at harvest are shown in Table 6.

In general plant weight increased as the proportion of grain in the substrate was increased. The overall effect of adding extra nitrogen was not significant but there was an interaction between the nitrogen treatment and the rate of grain. Nitrogen increased growth where the proportion of grains was 20% or lower but reduced growth when the percentage of grain in the substrate rose to 25 or 30%.

The overall performance of plants in the compost was encouraging. The control standard compost based on an inorganic fertilizer mix produced plants with a fresh weight of 53.2 grams. All the composts of the invention with a content of grain of 15% or more produced plants as heavy or heavier than the control. - 18 Table 6 : Growth of tomato seedlings in spent grain/peat substrates (grams/plant) Rate of grain (% by vol.) -N -j-N Mean 39.4 41.9 40.6 10 45.5 49.8 48.1 15 52.5 60.7 56.6 20 57.4 53.1 60.2 25 63.5 57.5 60.5 30 61.5 57.0 59.3 Mean 53.4 55.0 F-test S.E.(df=108) Rate of grain 1.4 Nitrogen NS 0.8 Interaction 2.0 Weight of control (inorganic compost) - 53.2 grams The nutrient levels in the composts of the invention without supplementary nitrogen are shown in Table 7. Also included are figures for the control inorganic compost and a substrate based on peat and spent mushroom compost (SMC) with an SMC content of 10% by volume. The good plant performance in the composts of the invention is probably explained by the adequate levels of nitrate nitrogen. A comparison between the spent grain compost and that based on SMC shows that the grain compost has much lower levels of K, higher nitrates and lower EC values. The low level of available nitrogen in the SMC compost means that this will be a factor limiting plant growth. The initial high level of nitrogen in the grains and the composting and ageing processes have resulted in the breakdown of the nitrogen compounds and the nitrification of ammonium to nitrate nitrogen. - 19 Table 7 : Nutrient levels in composts (mg/l, EC mS/m) % grain pH P K Mg no3-m EC 5 5.5 62 76 637 130 105 10 5.3 113 157 716 260 210 15 5.0 224 218 699 360 250 20 5.1 172 202 689 370 250 25 5.2 345 345 847 470 330 30 5.1 348 422 910 480 350 PG 5.7 165 374 571 155 125 SMC(10%) 5.6 170 890 754 63 260 It is important in a substrate to keep the electrical conductivity (EC) level to a minimum consistent with an adequate supply of plant nutrients (The EC is an indicator of the soluble salt level in a compost). High EC levels subject plants to water stress, delay and reduce seed gemination, retard seedling establishment and growth and can damage and even kill sensitive plants. In a commercial substrate, using inorganic fertilisers, waste ions e.g. Na which contribute to EC but are not needed in plant nutrition, are kept to a minimum and a specific balance of nutrients is precisely added. The PG compost has a relatively low EC but a good level of nutrients (Note that the nitrate level in the PG mix will double over time as over 50% of the nitrogen has been added in the ammonium form).

A substrate based on composted plant and animal waste has to accept the constraint imposed by the composition of the source material. This often results in substrates with low available nitrogen, high K and EC. The spent grain has however lost much of its soluble salts in the mashing process and has a relatively high nitrogen content. It therefore seems more suitable than other materials as a nutrient source in plant substrate. It is however very low in potassium and the - 20 addition of straw to rectify this may be advisable. The straw may also help to reduce the loss of nitrogen as ammonia during composting.

Example 6.

This example includes a number of illustrations of germination of seeds, and seedling development tests which confirm that a compost's performance is a function of the processes of this invention.

Test 1 A seed tray was divided in centre and one half filled with a commercial seed and potting compost, the other with Cl D137 (Cl compost at 137 days of maturity, see Example 4 for is manufacturing details). 160 Marigold seeds (var. Petite Mixed - Suttons) were distributed evenly on each half, sprinkled with more media, watered from bottom, covered and germinated.

Germination ....... 48% in Control 88% in CID137 Growing on ...... at 5 weeks, control seedlings were taller than CID137 seedlings which persisted to planting out at 3 weeks.

Comment. Excellent germination of seedlings in CID137 reflects absence of any inhibitory substances or contamination. Slower seedling development reflects a shortage of NO-j nitrogen which was llppm only in C1D13730 Test 2 Seed trays were filled (as in Test 1) with either C2D144, C3D130, C4D100 composts manufactured by processes of this invention (See Example 4 for details), or, control commercial compost as in Test 1.

These were sown with cress seeds. - 21 Germination compared with Control - 100% C2D144 - 99% C3D130 - 84% C4D100 - 89% Seedling Development at harvest (Day 22) Index (0-10, 10 is best) Control - 9 C2D144 - 5 C3D130 - 9 C4D100 - 5 Comment. Despite slightly poorer germination in C3D130 (84%), the excellent subsequent seedling development reflected adequate available nitrogen for cress. Slower seedling development in C2D144 reflects possible inadequate available nutrients, as would also be predicted for C4D100 according to the processes of this invention.

Example 7 The experiment compared composted black spent brewers grain and straw (DANU) with peat as a substrate for the growth of tomato seedlings in 11 cm containers. As nutrient sources in these substrates, a number of composted pale spent brewers grain were tested as three rates, 10, 15 and 20% by volume. An inorganic fertiliser was used as a control and a commercial peat compost was included as well.

Tomato seedlings were pricked out into these various mixes and they were grown on a glasshouse bench until the buds of the first flower truss were well visible. At this stage the plants were harvested and the fresh weight recorded.

The mean plant weights are shown below. For the pale grain fertilisers a mean of the three rates is shown.

Fert i1i ser Substrate DANU Peat _ Pale grain * straw (K) 17.1 20.3 Pale grain (K) 13.3 3.7 0900 15.1 20.0 0994 15.1 12.9 M600 21.8 21.0 PG inorganic + DANU 24.7 Commercial compost 35.3 While plant performance in the DAHU substrates did not match that of the commercial peat potting compost, it was as good as in peat for a number of the pale grain fertilisers tested. Where an inorganic fertiliser was used in conjunction with the DANU substrate plant appearance was a healthy dark green and plant growth was satisfactory.

Claims (14)

1. A process for preparing a compost comprising selecting the uncontaminated residues or by-products of the food or health care or 5 other products industries, admixing the selected by-products, forming the mixture into a heap and permitting aerobic fermentation of the mixture to occur characterised in that at least some of the by-products having been subjected to a heat treatment step in which the by-products are heated to at least 60°C for at least 30 seconds, the heat 10 treatment either being integral to or separate from the food or health care or other product production process.

2. A process as claimed in claim 1 characterised in that the heat treatment step heats the by-products to at least 150°C.

3. A process as claimed in any preceding claim characterised in that organic structural components are added to the mixture to optimise the carbon/nitrogen ratio to between 10/1 and 30/1. 20

4. A process as claimed in any preceding claim characterised in that organic structural components are added to the mixture to adjust the physical structure and/or porosity of the final product.

5. A process as claimed in claim 3 or 4 characterised in that the 25 organic structural component is selected from straw, bark and 1ignocellulose.

6. A process as claimed in any preceding claim characterised in that the moisture content of the mixture is adjusted to between 50% and 72% 30 (w/w dry matter).

7. A process as claimed in any preceding claim characterised in that the by-products are comminuted to a particle size of 5mm to 75mm. 35

8. A process as claimed in any preceding claim characterised in that the heap is aerated naturally, by forced aeration or by use of a . suitable reaction vessel. - 24

9. A process as claimed in any preceding claim characterised in that a microbial inoculant is added to aid composting.

10. An organic compost in which the raw materials or ingredients are 5 selected from the quality-assured uncontaminated residues or by-products of an established safe food, health or other production process characterised in that at least some of the by-products have been subjected to a heat treatment step in which the by-products are heated to at least 60°C for at least 30 seconds, the heat treatment 10 either being integral to or separate from the food or health care or other product production process.

11. A compost as claimed in Claim 10, characterised in that the ingredients are selected from brewers grains, brewers dark grains and

12. 15 pale grains, roast house and malt house dusts, traub and yeast residues, dried brewers grains, hops residue, distillers grain cake, draff, pot ale, pot ale syrup, grains syrup, distillers dried grains, distillers dried grains with solubles; sugar refining by-products of both beet and sugar cane origin; seed and cereal coats and polishings

13. 20 including wheat, oats, barley, rice, maize and sorghums, cereal extraction residues; residues from coffee extenders or cereal drink manufacturing; starch and sugar extraction residues; other alcohol fermentation residues such as corn distillers residues; other fermentation industry residues such as citric acid production residues;

14. 25 residues of microbial amino-acid production; secondary food processing and refining wastes; or by-products from health products industries, which have had intimate contact with the food or health product produced and which have subsequently not been undesirably concentrated or contaminated.