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I saw the following photo on my Facebook news feed:

I asked my friend who posted it for a source, and he gave me a link to a hemp manufacturer. I'm pretty sure it's not a reputable source. I'm interested to see if there is any independent study, patent, manufacturing process, etc, that shows this claim to be true.

Andrew Grimm
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Dang Khoa
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    It might take some searching to find a precise answer, but it does seem plausible. [Hemp fiber](http://extension.oregonstate.edu/catalog/html/sb/sb681/) is actually well suited to paper production but getting exact yields for both might be tough. – rjzii May 14 '13 at 14:59
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    I heard this claim in a Cypress Hill song. – Tom77 May 14 '13 at 15:44
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    If I remember right, tThere is a pervasive and false claim that hemp contains vastly more fiber per unit of mass than most other plants. In reality, hemp has a moderately high amount of fiber, but not amazingly so. This was due to a piece of incorrect info printed several decades ago and then latched onto by various hemp fans. If I can dig up the citations, I'll work it into an answer later. – Ask About Monica May 14 '13 at 21:15
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    I'm more interested in the "single season" part, trees grown in a single season aren't suitable for much, they need several years to grow (unless I'm really wrong here) – ratchet freak May 15 '13 at 08:11
  • based only on growing time and plant density, it seems quite plausible - though I also have no sources – warren May 17 '13 at 19:01
  • Over what time period? Are we talking a single harvest? or on an annual basis, if the acreage is re-planted with the same crop after harvest? – Flimzy May 23 '13 at 00:07
  • Related paper, with sources, but I don't have the time now to parse it into an answer: http://www.hemphasis.net/Paper/paper_files/hempvtree.htm – Flimzy May 23 '13 at 00:09
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    Bear in mind that yield per acre is only one factor in a whole suite of influences that determine whether a natural resource is suitable for a given task. How reliable is the harvest (resistant to weather and disease)? How hardy is the plant (farming range)? How easy is it to collect and process? And most importantly - in the eyes of the customer is it an acceptable product? Does hemp paper provide a pleasurable alternative to "tree paper" for the user? Answer "no" to any of those questions and the discussion is moot. – Drew May 23 '13 at 10:02
  • Well, apparently this quote is based upon an almost 100 year old study. Should we look at this from a modern standpoint or as things were 100 years ago? Given that people are trying to use it for modern arguments I'm inclined to say the former as opposed to the latter. – rjzii May 23 '13 at 19:50
  • One thing to keep in mind is that our current wood-based paper is a centuries old process which we have at this point - if not perfected, then definitely picked all the low-hanging improvement-fruit. Even IF wood gets better numbers than hemp, it is very conceivable that this is because we are just... more used to using wood. We are comparing a very mature technology to a procedure that nobody has been developing because planting the necessary crops is forbidden. – shieldfoss Jul 30 '13 at 07:48

2 Answers2

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This quote apparently comes from a 1916 USDA study on Hemp Hurds as a Paper-Making Material,

The most important point derived from this calculation is in regard to areas required for a sustained supply, which are in the ratio of 4 to 1. Every tract of 10,000 acres which is devoted to hemp raising year by year is equivalent to a sustained pulp-producing capacity of 40,500 acres of average pulp-wood lands. In other words, in order to secure additional raw material for the production of 25 tons of fiber per day there exists the possibility of utilizing the agricultural waste already produced on 10,000 acres of hemp lands instead of securing, holding, reforesting, and protecting 40,500 acres of pulp-wood land

Thus, this quote would have pre-dated modern manufacturing techniques for paper production as well as modern tree-farming techniques. This means that this is actually a difficult question to answer in part because tree farms and traditional farming techniques are completely different from each other and modern technology means that the techniques involved have likely changed greatly in the almost 100 years since the study was conducted.

To begin looking at things from a modern standpoint, tree farms typically thin a stand at 15 and 24 years with a final clear-cut harvest every 33 years (see slide 5 of 15). However, hemp can be harvested on an annual basis which puts it in line with traditional farm techniques1. This would imply that on a very simplistic level the hemp could come out ahead just because no thinning or harvest of a tree stand was done in a given year.

So to give a bit more of a fair comparison we are going to need to look at aggregate data and and look at the average yield per year. As with traditional farming different stands can result in different yields and in general harvesting sawlogs is more desirable than pulpwood (which is used to produce paper) since sawlogs are more valuable and therefore more profitable. This in turn means that stands tend to be managed with maximizing the amount of sawlogs produced.

The most commonly farmed trees for pulpwood appear to be Loblolly Pine, Acacia, and Eucalyptus with Eucalyptus being the most common. Based on my research, Loblolly Pine and Eucalyptus productions seem to be as follows:

The yields for hemp fiber3 on the other hand tend to be based more on historical data and tend to place the yields at 2 to 12.5 tons/acre/year with 5 tons/acre/year being the average on a good year. A modern report from a Kentucky farm put the yields at 2.8 to 6.1 metric tons/acre/year with other sites getting worse yields.

Thus, to return to the original claim, if we assume that only paper production is considered (i.e. fiber production in the case of hemp and wood pulp production in the case of trees) then the claim appears to be false with hemp yields only appearing comparable to Loblolly Pine per acre/year wood pulp yields although it is possible for hemp to out produce Loblolly Pine production when it is not grown for pulpwood.

However, if other trees are considered then well managed tree farms appear to greatly outproduce hemp farms in terms of per acre yields. The only way this claim is true is only if year-by-year data is examined due to the way tree farms are thinned and harvested due to the significant number of years of no production.

  1. For our purposes this is being defined as mechanically assisted farming with harvest being done at the ideal time to maximize yield.
  2. Green ton - 2,000 pounds of undried biomass material.
  3. This is also assuming the fiber is only used for paper production as opposed to other usage in clothing or rope production.
  4. Some useful timber volume-to-weight conversions.
rjzii
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  • I think you missed a step. After you harvest the wood you have to reduce the pulp. And then Yield the paper. The claim is not about the weight of much raw unprocessed source their is but rather the yeild of the finished product. – Chad May 23 '13 at 18:06
  • @Chad - Indeed, but if the woodpulp yield is low then you aren't going to get more product out of it than you put into it in raw materials. – rjzii May 23 '13 at 19:03
  • My point is you are comparing raw material quantity instead of yeild. The claim is that an acre of hemp will yield more paper than 4 acres of trees. – Chad May 23 '13 at 19:29
  • @Chad - Sure, but finding the quantity of woodpulp needed to produce paper has actually been very had to answer as most of the answers are very "hand-wavy" since they tend to be in terms of "x tries to ream of paper" which introduces painful conversions. However, at the end of the day nothing I found implied that you can get more out than you put in (i.e. one ton of woodpulp produces one ton of paper) or at best the manufacturing loses were fairly minimal to the process. – rjzii May 23 '13 at 19:43
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    If you included a source with that information then I think you have a good answer. You are just one step short right now imo – Chad May 24 '13 at 12:49
  • @Chad - I've been looking for one but it seems to be quite elusive as most of them are the "trees to reams of paper" type maths as opposed to "tons of woodpulp to paper. – rjzii May 24 '13 at 13:21
  • See also: http://www.adm.uwaterloo.ca/infowast/watgreen/projects/library/f98treevshemp.125.pdf –  Jan 28 '16 at 07:11
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No it doesn't.

There are several reasons why hemp is not used to make paper. Biggest one is that it's more expensive.

Hemp has never been used for commercial high-volume paper production due to its relatively high processing cost.

The cost of hemp pulp is approximately six times that of wood pulp, mostly because of the small size and outdated equipment of the few hemp processing plants in the Western world, and because hemp is harvested once a year (during August) and needs to be stored to feed the mill the whole year through.

While the wood products industry uses nearly 100% of the fiber from harvested trees, only about 25% of the dried hemp stem — the bark, called bast — contains the long, strong fibers desirable for paper production.

Hemp is only harvested once per year. And the hemp need to be stored for quite a while. Storing costs together with the fact that only a small part of the hemp can be used for paper, makes hemp not overly suitable for paper, economically.

Yields of hemp farming

Cultural requirements and production costs are quite similar to those of corn. Reported hemp yields range from 2.5 to 8.7 tons of dry stems per acre.3

Yields of wood

In the paper they use fast growing types of wood, and get a yearly yield of between 6 and 12 tons per year per acre.

Other paper

Production Rate per Acre: 6.9 green tons

Wood uses much higher efficiency converting wood to paper than hemp to paper. 1/4th vs close to 100%. Yields of wood per acre per year, is similar and sometimes more than the ones of hemp.

The picture is wrong, seeded forest is more efficient for paper than seeded hemp. Hemp is less efficient than wood, and doesn't give substantial better yield per acre per year, and is not as economically favorable as wood either.

All in all, wood and foresting is most efficient way to gain paper, per acre.

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Wertilq
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    This is an interesting answer; it surprises me. But it needs better references. Rather than Wikipedia, why not go to the original sources? "Yields of wood" link is for wood pellets; are they used in paper-making? Where do you get the efficiencies from? – Oddthinking May 23 '13 at 11:52
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    Also, hemp only being harvested once a year isn't really a point against it considering that commercial tree farming has an odd harvesting schedule, as per your source, 15, 24 and 33 years. Plus, does the four acres apply to clear cutting or selective harvesting techniques? Also, yields for wood seems to be highly variable, one of your citations says 2.0 tons/ac/year for pulpwood which is used for paper products which would be below the hemp yields. A good start but it needs a lot of work still. – rjzii May 23 '13 at 12:00
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    okay I will give this answer a major work-over, and not use wikipedia for any part, and find more info about efficiency, and I will write down more details about the techniques used for harvesting the hemp and the wood, and which type of forest it is. – Wertilq May 23 '13 at 12:22
  • Wikipedia is fine for some parts where it is acting as an aggregator or summary but for more specialized information it can be dubious versus most specialized sources. Also, I'd avoid focusing on comparing costs of production and just on the actual yield for acre that could be used for paper production. Historically hemp was preferred over paper and it wasn't until cheaper wood pulping techniques were discovered that the costs went down. There's nothing saying that the same couldn't be done for hemp in the future. – rjzii May 23 '13 at 12:25
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    @RobZ I think the point is that you can only harvest hemp in October, so you must do all of your harvesting then and then store it for the rest of the year. You can harvest trees at any time, as long as you rotate your harvest area, so you can have continuous production with minimal storage. – Ian May 23 '13 at 15:48
  • @Ian I'm confused, the point of the question or the point of one of the comments I made? – rjzii May 23 '13 at 15:58
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    @RobZ the answer lists that fact that "Hemp is only harvested once per year" as a disadvantage because it requires you to store it for the other 11 months. You commented "hemp only being harvested once a year isn't really a point against it considering that commercial tree farming has an odd harvesting schedule". What I'm saying is that it's not about the gap between harvests, its about how often you can harvest within a year. i.e with trees, as long as I've got enough of them that it takes me 15 years to get through all of them then I never have to stop. I can't harvest Hemp in winter/spring. – Ian May 23 '13 at 16:13
  • @Ian Alright, I see what you are saying, but on the same token, you are also assuming that the trees are mature enough to be harvested. A newly planted acre isn't going to be mature enough for any sort of harvest for a couple years where as you can get the hemp harvest the same year you plant it. 15 years from the original planting appears to be the earliest that you can realistically harvest trees which is a long to time to wait to have paper. – rjzii May 23 '13 at 17:24
  • I would like to see a source on the efficiencies. I think that if you have a good one then you have the important part to compare. – Chad May 23 '13 at 18:12
  • [This](https://www.google.com/maps/@45.7681341,-119.5435543,12296m/data=!3m1!1e3) is what a modern pulpwood farm looks like (I believe this one's growing poplar). I count about 150 plots spread out over 36 or so square miles, which works out to a harvest every few months. – Mark Sep 24 '15 at 00:14