Whenever I speak to university and high-school audiences the subject of hemp is high on the list. It seems that many young people have been convinced that we should stop cutting trees and use hemp instead. All in the name of saving forests and preserving biodiversity. Hogwash! While hemp makes perfectly good paper and cloth, it is an exotic annual farm crop that requires land to grow, land that could otherwise be growing trees. Most of the statements made about its superiority to trees are myths with no basis in fact.
Here is an excerpt from an advocate of hemp. He is trying to put a good face on it but there is just no getting around the fact that hemp uses more nutrients than most other crops. It requires heavy fertilization or four-year rotations.
“Hemp grows best on rich and fertile, neutral or slightly alkaline, well-drained clay-loam or silt-loam soils in which the subsoil is fairly retentive of moisture. Although hemp makes heavy nutrient demands on the soil, research conducted at Canadian experimental farms during the 1930s showed that hemp takes less from the soil than wheat or corn when taking into account that up to 70 per cent of the nutrients absorbed by the plants are returned to the soil, in particular with the large numbers of falling leaves and through the retting process. Cleaning or mechanical stripping of the leaves and flowers in the field also allows for maximum nutrient recycling. However, prior to the nutrient recycling, hemp extracts more nutrients per hectare than grain crops, removing about two to three times as much nitrogen, three to six times as much phosphorus, and 10 to 22 times as much potassium per hectare, owing to fast biomass production.
Therefore, to achieve an optimum hemp yield, at least twice as much nutrient must be available in an easily assimilable form as will finally be removed from the soil by the leaf-free harvest. Fertilizer rates vary depending on soil type, end use of the plant and crop rotation. A three-year, but preferably a four-year rotation, such as cereals, clover for green manure, corn, hemp and then back to cereals is recommended to help maintain soil fertility.”
Source: Government of Canada, Agriculture Canada: Report on Hemp, Bi-Weekly Bulletin, December 16, 1994 Vol. 7 No. 23, by Gordon Reichert.
It is clear from this that hemp is very demanding on soils and will require both heavy fertilization and long fallow periods between crops.
This is an excerpt from my book, Green Spirit, on the subject of hemp.
Some environmental groups argue that because it is wrong to kill trees to make paper we should make paper from something else. They suggest substituting hemp and kenaf. Hemp is the plant from which marijuana and hashish are derived. It was formerly used for making ropes (Manila hemp) and sacks before being replaced by petroleum-derived substances such as nylon and polypropylene. Kenaf is a member of the hibiscus family. Both hemp and kenaf originate from the far-eastern sub-tropics and contain excellent fibres that can be used to make fine paper products. The advocates of this proposal believe that we should embark on a vast program to replace wood with these crops as our primary source of paper products.
I recently attended a reception for Robert Kennedy Jr. of the Natural Resources Defense Council in a small art gallery in a trendy part of New York City. I found myself standing with a group of environmental activists who were having a lively conversation about the desirability of wood-free paper. A young woman reported that she was hoping to get tobacco farmers to grow kenaf instead of tobacco, with the apparent intention of earning double eco-points by simultaneously saving trees from death and people from lung cancer. “Wouldn’t it be better,” I offered, “to plant trees that are native to the area and use them to make paper? In that way the tobacco farms could be put back to something like the original eastern hardwood forest.” To this came the quick reply, “People can’t plant a forest, only nature can produce a forest. People can only plant trees.” Surprised by this I tried again: “But surely it would be better to plant native trees than some exotic sub-tropical annual farm crop that needs pesticides and fertilizer. Birds and squirrels would like trees more than kenaf.” This line of reasoning got nowhere. When I suggested that if all the paper derived from wood had to be replaced with wood-free paper we would end up deforesting vast areas of the continent to get enough land to grow hemp and kenaf, my listeners’ eyes rolled back and I could see I was dismissed. It amazes me that some people can’t understand that if you don’t use trees to make paper and other forest products there is less reason to plant and grow trees. The next thing you know there will be a campaign for “tree-free wood.”
There is a similar movement to substitute hemp for wood in Australia. Research has been done there as well. Here is an article that appears on the web-site of the National Association of Forest Industries. I recommend this site for a wide range of forest issues and a glimpse into another country’s debate over forests.
The Hemp Alternative – more hype than substance
by Heike Von Der Lancken
Forest Protection Society
Opponents to Australia’s native forest industry often raise the issue of growing hemp as a replacement for wood to produce paper and other wood products. Recently, the debate has resurfaced in the media, with the Victorian Government planning to set up a multi-million dollar industrial hemp processing industry in north-eastern Victoria.
The South Australian Government has come under fire for not taking the initiative in setting up a hemp industry first, already having run a trial program. The problem, it seems, is that the trials failed, leaving the SA Government a bit nervous about the viability of this industry. And not without good reason, either, it seems.
A conference on the potential of an industrial hemp industry in Australia (convened jointly by the Institute of Agricultural Science and the Rural Industries Research and Development Corporation at the end of 1995) concluded that at present it was not economically feasible, nor was the right technology available to establish a broad area hemp industry in Australia. The best that proponents of a hemp industry could hope for was a small regional or cottage industry.
Research and evaluations of hemp by scientists at North Forest Products have found these and a significant number of other reasons why hemp is not as viable an alternative to eucalypt as is oftentimes claimed by those opposed to logging:
Hemp is very demanding on the environment
Any crop requires a period of establishment, during which time the site is cultivated and weedicide added, until the crop takes hold of the site. For hemp this site disturbance will happen at least once a year; for eucalypts only once per rotation; which, in the case of eucalypt tree farms, may vary from 10-25 years • hemp would require large areas of fertile, well-drained land, and probably irrigation, even in Tasmania. This would be expensive and compete for land and other resources with other intensive crops, dairying, etc.
Eucalypts and hemp have similar growth rates measured as dry material per year. However, for quality papers, only the outer (bast) fibre of hemp can be used. This grows at one to three tonnes of useable pulp per hectare per year; whereas eucalypt grows at four to seven tonnes per year.
The fibre is unsuitable for the large majority of market requirements
A wide range of non-wood plant material can be used to make paper, including sugar cane, straw, corn stalks and grass. However, the quality and cost of pulp will determine which grades of paper are viable from any given species. • The properties of hemp are such that it cannot be marketed as equivalent to eucalypt kraft pulp, which represents the major market opportunity; • The extreme length of hemp fibres means that they require special handling and pulping equipment and cannot be used as feedstock to mills designed to use woodchips. • Hemp would need to be used in a small new mill, to produce a filler pulp for speciality papers.
Growing and harvesting of hemp presents a number of logistical problems.
Harvesting for eucalypts is a year round activity, but for hemp would be very seasonal. This presents a number of labour and financing problems and would compete with other crops for the availability of machinery. • Eucalypts can be “stored’’ on the stump after growth has occurred. Hemp would require large volumes of material to be stored under weatherproof conditions, for long periods, to cover the period between harvests and to smooth variation in availability due to differences between seasons. • Compared with eucalypts, hemp is a very bulky crop and would be correspondingly expensive to transport. Transport cost, particularly in Australia, is always a major portion of the total cost of fibre supplied to a paper mill. There would be associated pressures to have an estate concentrated in the vicinity of the mill. This may generate problems in reducing the diversity of the landscape.
A few other interesting facts about hemp and hemp production are:
Hemp pulp costs $US2,500 per tonne compared to $US400 per tonne for typical bleached wood pulp; • hemp grown in Europe is subsidised by the EU at $US900/ha; • Trial plantings of hemp in Australia appear to yield between 1 and 12 tonnes/ha dry stem (per year). This is dependent on rainfall/irrigation. Depending on the processing model used, the gross margin to the grower after some farm processing ranged between a loss of $59.75 to a profit of $1,100 per ha. Cash crops generally yield $4,000 to $10,000 per ha gross margin.
All of which is worth making a mental note of for when next someone asks the question “Why can’t we grow hemp instead of chopping down trees?’’.