Re: why didn't colonial americans make alcohol from maple sap?

As a homebrewer and a biochemist, I know that a tasty sort of "maple mead" can be fermented from maple syrup (although this is not distilled, like rum), so my first impression in thinking about your question was that the answer would be more economic than biochemical. With that in mind, I crunched the following numbers about the production of sugar from maple syrup and sugar cane.

Maple syrup is obtained by tapping (obtaining sap from a hole bored through the bark) a sugar maple during a short period of time in the spring. Depending on the tree's size, a sugar maple can support from one to four taps, and a modern sugarbush (aka, a sugar maple orchard) can support somewhere between 50-80 taps per acre each year. Each tap yields about six to ten gallons of sap. About ten gallons of sap are boiled down to one quart of syrup, so an acre of sugarbush can produce 30-80 quarts of syrup.

The "sugar" in both maple syrup and sugar cane is primarily sucrose, a disaccharide composed of glucose and fructose. To determine the concentration of sucrose in a quart of maple syrup, I took a look at the back of the bottle of "real maple syrup" in my kitchen, and I also did some calculations based on the boiling temperature of maple syrup. The bottle in my kitchen said that there were about 2.32 moles of sucrose per quart of syrup. Syrup boils at 219.1 degrees Fahrenheit, which tells me that there are about 1.84 moles of sucrose per quart.

A mole of sucrose weighs about 364 grams, which means that we get about 1.5 to 1.8 pounds of sucrose per quart of syrup. Plugging this in with the production of 30-80 quarts of syrup per acre, we can obtain a maximum of almost 150 pounds of sugar per acre of sugarbush, but the yield can also be much lower.

Cane sugar is obtained by crushing sugar cane plants, extracting the liquid and then evaporating the liquid portions, leaving behind crystallized sucrose. Modern sugar cane processing methods yield about one pound of sugar for every ten pounds of cane, and modern sugar cane plantations can produce 30 to 40 tons of sugar cane each year. So, a modern plantation can easily produce three to four tons of sugar per acre.

Now, these numbers are for modern methods, but what about colonial times? Maple syrup production increased sharply during the middle of the 19th century (i.e., before and during the Civil War), when lidded metal buckets were first used to collect the sap. Prior to this time, buckets were uncovered, and the sap had to be strained to remove impurities. Modern high-volume sap production facilities have done away with the buckets entirely and use hoses and reverse-osmosis facilities to concentrate the syrup, but it looks like maple syrup production on modern scales began in the middle of the 19th century; prior to that, sugar yields were probably much lower.

Nineteenth century sugar cane facilities were not nearly as efficient as modern facilities. Sugar cane plantations could produce up to 1600 pounds of sugar per acre, but not all of them did so. Still, 19th century sugar cane sucrose production outstrips 21st century sugar maple sucrose production by more than a factor of 10, and it seems likely to me that this tremendous difference in productivity would hold true for colonial methods as well.

Some additional factors need to be considered. A sugar cane crop can be harvested in 12-16 months after planting, while sugar maple trees can take 35-80 years before they are ready to be tapped. In addition, the size (and therefore the age) of the tree determines how many taps it can support, so it might take up to a century before a "new" sugarbush is producing sap at peak efficiency. Finaly, sugar maples are only useful as sap producers when they are grown in a climate where there are hard freezes at night followed by temperatures above freezing during the day. A large colonial initiative to send maple trees to Europe failed because these conditions are not found in Europe. This would limit the productive range of the sugar maple in North America as well. Sugar cane on the other hand, has spread all over the tropical world.

So overall, it seems like any sort of maple syrup fermentation industry would be hard pressed to compete with the sugar cane liquor fermentation (i.e., rum) industry.

Here is some information about the modern maple syrup industry.

Maple Syrup Industry in Ontario, and Ohio State University Fact Sheet: Hobby Maple Syrup Production.