Hemp: The Technical Obstacles

An evaluation by David P. West Ph.D.

Please note: This essay is 20 years old.

There is a great deal of enthusiasm for the potential of the hemp crop. The anticipated benefits of the crop extend as far as saving the planet. No doubt a laudable goal, but meanwhile, those who are involved with the implementation of the vision face several significant near-term technical obstacles. The historical context of our current situation has been developed in other writings. In short, we have lost the hardware, savoir faire, and seed varieties on which the earlier industry was based.

The Hardware:

Hemp's primary use in the old days was as cordage. Its new uses will be in medium density fiber board, as a pulp source and textiles. Technical developments in fiber handling have progressed such that new machinery would be needed in any case, so this loss is not significant. As a replacement for wood in resin bonded fiberboard, new hemp field harvesting approaches are needed. Equipment used in kenaf will probably be suitable. Hemp can be planted with existing equipment. The plant itself may need breeding for different phenotype.

The Know-How:

Very few people are still living in North America who have actual experience with growing hemp. Agronomically, the crop is not difficult, and its benefits to the rotation in terms of weed control have been discussed elsewhere (See: Hemp as Weed Control).

Critical technological solutions are needed for the harvest and post-harvest handling of the crop. Old systems are probably no longer practical, it was still too labor intensive even in the Forties. The old process of field retting will probably be abandoned. Specialized techniques appropriate to the particular end use--board, textiles, paper--must be developed. In this regard the loss of the old is, again, not particularly serious. Approaches to these problems are progressing in Europe.

The Seed Varieties:

In most of the world with the exception of Europe, CIS, China and Chile, there is no adapted improved fiber hemp germplasm. North America has feral material which is in need of collection and evaluation, but is unlikely to be immediately useful for commercial production. Chile and China have landraces which have not been bred in a technical sense and have fiber contents in the 12-15% range. This is the "natural" fiber content of unimproved hemp and is similar to that found in feral hemp in the US.

Breeding programs for hemp have operated in Europe and CIS. The most aggressive breeding work has been done in France and Hungary. The French program (as well as several others, e.g., Germany, Poland, Ukraine) emphasized monoecious varieties. The Hungarian program has focused on dioecious types and hybrids. Fiber percentages in improved varieties are generally above 20%, reaching into the low 30%.

The hemp grown previously in North America was dioecious. The industry in the twentieth century in Wisconsin used seed grown in Kentucky. This material did not flower in Wisconsin. Breeding was done by the USDA which resulted in several improved varieties. All of the improved North American germplasm has been lost. Kentucky Hemp, the generic type grown most commonly in the US, has not been maintained (See Fiber Wars).

Hemp is now returning to many areas of the globe where there are no adapted varieties, for instance, Canada, Australia, Argentina, South Africa and eventually the US. It has been necessary for experimenters in these areas to import seed from the European programs and the results have naturally been lackluster. European hemp was grown in the US until the middle of the last century when it was learned that Chinese varieties performed better (See: Fiber Wars).

Hemp is generally grown in Europe at more northern latitudes than regions in the US where the crop would be grown. The maturation period of hemp bred there is thus short for here; in other words, varieties from Europe will flower too early.

Heretofore, hemp has not received the attention and technology that has been applied to a modern crop such as, say, corn (maize). Although the crop is naturally dioecious, hybrids have only been developed in one breeding program, that of Bocsa in Hungary and so far very little inbreeding has been done.

Corn (maize) has parallels which are instructive. At the same time that two previously separated germpools (genetic groups) of Zea mays were meeting in the American midwest, an event which gave rise to new genotypes which are the basis of today's modern hybrid corn industry, the Chinese and European hemp germpools were meeting in Kentucky. From that fusion arose Kentucky hemp. Lyster Dewey perfected open pollinated Kentucky hemp into several varieties, most notably Chinamington. Chinamington was used as one side of the first hemp hybrid, that developed by the Hungarian hemp breeder Fleischmann. (Kompolti, an Italian derivative, was the other side of the cross). Today, in Hungary, Professor Ivan Bocsa has developed some new hybrid types.

This is as technically advanced as hemp breeding has become. Breeding in hemp is also burdened by the requirement for THC screening as a primary criterion for variety registration.

So far there is no genetic map of the crop. Biotechnology has been little applied. Inbreeding, as is universally employed in the development of corn lines prior to crossing to make uniform, high performing hybrids, is difficult in hemp and has not been emphasized. The genetic load of the crop is thus probably quite high, which would indicate opportunity to significantly improve the crop's productivity.

Traditionally in Wisconsin, hemp yielded approximately 3 tons dry matter per acre. Today, silage corn in Wisconsin produces 6 to 9 tons dry matter per acre. The productivity of hemp can be substantially increased with the application of modern breeding techniques.

The success of the crop as a replacement for other fibers is directly dependent on its biological productivity. The initial experience of hemp enthusiasts as they begin growing this crop may be disappointing while they depend on European sources.