Stop - Huletts " Stalk Only Please

The results obtained from 17 030 samples of cane taken by grab samplers at five Huletts mills during the 1975176 season were analysed for extraneous matter. They indicate a mean of approximately 10 0/, on gross cane. The benefits of a reduction to 7 % are estimated and a proposed programme to achieve this target is outlined. Introduction Oliver Lyle in one of his entertaining and highly informative books wrote "Sugar cane is a gigantic grass and consists of roots, stalk and leaves". This is an adequate description of a great deal of cane delivered to Huletts mills, plus sand, mud, scrap iron and rocks at times. The milling companies would much prefer only to receive the stalk and a great deal of trouble is caused by processing the other components of our cane deliveries. Looking at the problem Huletts decided to draw up a programme which it is hoped will lead to a reduction in extraneous matter delivered to their mills in the not too distant future. Basically, the programme was : (i) to define the problem. It was decided there were two distinct problems, cane with too much trash and tops on the one hand and cane with too much sand, rocks and mud on the other, with the occasional chunk of metal for good measure. It was decided to concentrate on cane kith too much trash and tops for two reasons: (a) trash and tops could probably be measured fairly easily. (b) success in getting cleaner cane would probably solve the second problem to some extent. (ii) to carry out a literature survey on the subject of poorly cleaned cane. This was done and a surprising amount of study has been carried out, and numerous papers prepared. (iii) to introduce systems to measure the amount of trash and tops being received at Huletts mills. This was done at five mills as described later. The object was to measure the present problem and to collect base data for later comparison. (iv) to evaluate the cost of the problem in order to get some idea of how much Huletts are losing by processing trashy cane. (v) to propose a possible method of minimising the problem. It is not anticipated that it will be eliminated in the foreseeable future. PROGRAMME Literature survey Several aspects were covered and some worth mentioning are as follows: The analysis of the tops and trash bear little relation to the stalk they accompany. Studies conducted by Arceneaux and Davidson2 indicated that the dry matter from green trash contains more than twice as much soluble solids as does the same quantity of dry matter from dry trash. Keller and Schaffer4 found that an increase in trash of 1 % increased the fibre % cane by 2,75%. Arceneaux and Davidson2 fouhd that sucrose losses in bagasse due to the presence of trash could increase by as much as 33%. This figure applied to South African mills would result in a change of 2 % in mill extraction. They also found that trashy cane contributed molassegenic non-sugars to the juice with consequent increases in molasses losses, and that the efficiency of imbibition was decreased. The effect of trashy cane on the efficiency of diffusion plants has yet to be studied but we suspect that it is significant. Tests in Taiwan,lo where an industrial quality control programme has been in use for many years, indicate that overall recovery is reduced by 0,34% for every increase in trash of 1 %. Many other factors were discussed in the papers surveyed, such as wear and tear on plant, reduced capacity, increased cane transport costs, and a comparison of cane harvesting and loading systems (push-pile loaders and grabs showing some appalling figures for extraneous matter content). Sampling and measuring extraneous matter The principal difficulty associated with the sampling of cane is the inherent heterogenity of the material. Cane delivered to the factory can best be described as a "tangled mass", the ability to withdraw representative samples from which poses problems. The hatch sampler produces a representative sample suitable for the determination of the simple constituents of cane such as pol, brix and fibre. However, due to the considerable preparative effect of knives the hatch sampler is not TABLE 1 Analysis of Typical Clean Cane and Extraneous Matter Note that while tops are not good for processing, trash is very much worse. TABLE 2 Percentage of Dry Matter, Fibre and Soluble Solids in Dry and Green Trash Fibre %