The Kurth Kiln is a charcoal kiln and associated storage shed, located on Soldiers Road, approximately north of , on the Tomahawk Creek, within the Kurth Kiln Regional Park, in the Yarra Ranges, in the north eastern suburbs of Melbourne, in Victoria, Australia.
Built between 1941 and 1942 by the Forests Commission Victoria on the traditional lands of the Wurundjeri people, the kiln was added to the Victorian Heritage Register on 20 March 2003 in recognition of its historical and scientific significance; and was also added to the non-statutory and now defunct Register of the National Estate on an unknown date.
The site is managed by Parks Victoria as part of the Kurth Kiln Regional Park; and is open to the public.
History The Kurth Kiln was constructed by the Forests Commission of Victoria between 1941 1942 to produce charcoal for use as a substitute fuel source. Petrol shortages during World War II created a demand for charcoal suitable for gas producer units fitted to cars and trucks. The Kurth Kiln was the only commercially-sized continuously operational charcoal kiln in Victoria. The kiln was in full production by mid-1942, but transport difficulties, structural problems, and oversupply of charcoal by private operators meant the kiln was used only intermittently during 1943, and was shut down soon after. The kiln is one of only two known portable metal charcoal kilns in Victoria.
Dr Ernest Edgar Kurth from the University of Tasmania was commissioned to design the kiln. Gembrook was selected as the ideal site for the kiln because it fully met three essential criteria required for successful operation that included: water — the kiln required of water per day in order for its cooling systems to be effective; wood — the kiln burnt approximately of wood per week; and gradient — sloping land enabled easier-top loading of wood into the kiln.
Dr Kurth was paid A£5 for the use of his patented design and the total cost of establishing the kiln was A£1,799, seventeen shillings and tuppence. The kiln commenced operation in March 1942 but transport difficulties combined with an oversupply of charcoal from private operators meant the kiln was used only intermittently during 1943 and was shut down soon after. Over the period of its operation, Kurth Kiln produced only of charcoal, which represented a tiny fraction of Victoria’s total production.
Petrol rationing
Australia’s declaration of war on 2 September 1939 immediately raised concerns about the security of petrol supplies. At the time Australia was totally reliant on imported fuel and had a limited storage capacity. At the start of the war, the country had sufficient petrol for only three months supply and by May 1940 the Commonwealth Oil Board estimated that only 67 per cent of the total capacity of approximately was on-hand.
The Australian Government considered increasing the price of fuel to dampen demand. Another plan was that petrol should be merchandised in two colours, blue for commercial vehicles, and red for private cars, with red petrol being substantially more expensive than blue. The motoring industry and newspapers resisted the changes. When France collapsed, the Minister for Supply stressed to Cabinet that continuity of the already erratic deliveries was under threat, and on 6 June 1940 Cabinet made the decision that rationing should be introduced to reduce consumption by fifty per cent. Political expediency came into play and petrol rationing was introduced in September 1940 and restrictions were tightened as the war progressed.
On 17 June 1941 the Prime Minister, Robert Menzies announced further restrictions to motorists limiting them to per month which were enough for per year so many simply put their cars up on blocks for the duration and switched to public transport or walked. The scheme devised for petrol rationing coupons was complicated, and the paperwork was profuse. Drivers had to apply for a petrol licence from which they were allocated ration tickets based on an assessment of their needs.
The firefighting vehicles operated by the Forests Commission were exempt from the petrol restrictions. District foresters were authorised to issue petrol coupons for timber industry trucks, which, in the absence of private cars and utes, often served as family transport too. Country school buses were fitted with gas converters and on declared days of Acute Fire Danger they were banned. Some of Melbourne's buses also ran on charcoal. Petrol rationing was not strictly enforced until 1942 but remained in place until February 1950.
Charcoal as a replacement fuel
During the first half of the twentieth century charcoal production in Victoria was small and employed relatively few people. The charcoal was supplied to blacksmiths, coal depots, gas works and some powerhouses. The main areas in Victorian state forests that produced charcoal were in a broad arc across Central Victoria, including , , the Dandenongs, Gembrook, Lionville, , and . Charcoal was also produced in East Gippsland, mainly at . The best trees were durable species like red ironbark (Eucalyptus sideroxylon), red box (E. polyanthemos), grey box (E. microcarpa), yellow box (E. mellidora), red gum (E. camadulensis) and for lighter grades of charcoal, yellow stringybark (E. meullerana).
The charcoal was produced by slow and controlled burning of wood in earthen, brick or metal kilns. The simplest method was the beehive kiln where wood was stacked vertically into a conical heap to allow air and smoke movement and then covered with a layer of sticks and twigs. The stack was then covered further with a thick layer of earth and ash. Once the stack was alight the small chimney opening at the top was sealed. It then required constant tending to ensure no air entered the stack and took approximately three days to reduce the wood to charcoal. Large beehive kilns each contained approximately of wood and were very labour intensive. They also produced charcoal of uneven consistency with a high ash content and some inevitable soil contamination. Other charcoal producers opted for lined pits in the ground, steel chambers, or recycled boilers.
With the urging of the Australian Government, charcoal quickly emerged as a substitute fuel in response to the national petrol rationing. A special vehicle-mounted unit which converted charcoal into flammable gases (principally carbon monoxide and hydrogen) was known to be suitable to power internal combustion engines.
Charcoal was relatively simple to produce but had a well-deserved reputation for being inconvenient to use for short trips, inefficient, under powered, dirty, belching black smoke, catching fire and occasionally exploding. Also, the cost of installation of a heavy and cumbersome producer gas kit was approximately A£100, or the equivalent of 16 times the average weekly wage, and a bag of charcoal lasted between at a cost between 6 and 10 shillings. Charcoal had a cost advantage over petrol and tests earlier in 1938–1939 indicated savings in the order 80 per cent for truck operations for producer gas compared to the cost of petrol. At the time, a new car, if you could get one, cost approximately A£250 for a small Austin, and A£525 for a large Buick.
Over the war-years, some 56,000 gas producer units of varying design were fitted to private and commercial vehicles in Australia. This low conversion rate to producer gas technology represented less than 6.5 per cent of all vehicles on the road by 1944.
The overall consumption of charcoal in Victoria rose thirtyfold from approximately per month before the war to over by mid-1942. This massive increase required nearly s of dry wood annually to feed the hundreds of kilns set up across State forests, as well as on private land, at a time when labour was critically short.
Forests Commission Victoria The task of ensuring adequate supplies of charcoal fell to the Forests Commission Victoria. It subsequently formed the State Charcoal Branch to organise the increased production of charcoal, to build up reserves to meet emergencies and to regulate the cost to consumers. The assistance of an expert Advisory Panel, representing charcoal producers, manufacturers and distributors of vehicle gas equipment, the Department of Supply and Development, and the Victorian Automobile Chamber of Commerce, was enlisted under the Chairman of the Forests Commission, Alfred Vernon Galbraith. Preliminary arrangements were made for bag supplies, for railway sidings in Melbourne, and for processing of charcoal bought by the Branch in excess of the requirements of private grading firms. In its first year, of charcoal were produced compared with before the war. Production peaked at in 1942-1943.
The Commission had the added responsibility of providing emergency firewood to Melbourne for heating and cooking purposes as a result of reductions in the supply of coal, electricity and gas. The Emergency Firewood Project continued long after the war ended and over the period from 1941 to 1954, nearly of firewood was produced.
An estimated 221 kilns and twelve pits were producing charcoal by the middle of 1942. Some of the labour was provided by Italian wartime internees. There were also over 600 commercial kilns operating mostly on private property. At least 50 to 60 private charcoal retorts were set up in the Barmah forest alone. The majority of the kilns were metal retorts because charcoal from earthen beehive kilns or unlined pits proved unsuitable for motor vehicles, causing gumming of engine valves and the controls in the gas lines due to the condensation of tar.
Galbraith became aware of experiments by Dr Kurth, who had been experimenting with the pyrolysis of wood and kiln designs since 1940. Kurth's work led to a quarter-size prototype kiln at Dover, Tasmania in March 1941. A second operational kiln was built at a sawmill near Launceston in January 1942. In July 1941, Professor Kurth provided details of his kiln design and nine pages of handwritten notes on its operation to Galbraith which marked the beginning of the project at Gembrook.
The kiln was unusual in that it could operate continually with the top loading of wood billets and bottom recovery of charcoal. A water-cooled grate at the bottom of the stack caused the brittle charred wood to crumble under its own weight into manageable pieces, while at the same time maintaining the charring temperature at the critical point to produce a consistent quality charcoal. Not only was this process said to be 50 per cent faster than any other method then in use, but it was also 10-15 per cent more efficient. So cooled charcoal was raked out the bottom as more wood was added into the top.
Tests in Tasmania indicated that the prototype could produce approximately of charcoal per day which compared favourably with a single ton every three days from a standard steel kiln. of wood produced of charcoal with an output of per week if the kiln was operated continuously with three shifts per day. The cost of building the kiln was estimated to be approximately half that required for five or six portable steel kilns needed to produce the same quantity. Good quality charcoal sold for four shillings and sixpence for a bag. The claimed advantages could not be ignored by an organisation under pressure to secure Victoria's war-time charcoal supplies, so Galbraith enclosed £5 to Professor Kurth in a letter on 16 July 1941 for the use of his patented design.
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