Moisture Content in Biofuels

The moisture content in a biofuel determines the amount of air required to attain optimum heat to burn the material for energy use. If a biofuel is mixed with too little or too much air, it can burn too rapidly or incompletely. The proper guidelines for measuring moisture content in biofuel materials are addressed in ISO 18134:2015 – Solid biofuels - Determination of moisture content - Oven dry method.

Biofuels are the energy sources made from living things or the waste that living things produce. Much of the gasoline used in the United States is blended with the biofuel ethanol, which is generally created from heavily-processed corn. Fossil fuels like gasoline and diesel are technically ancient biofuels, since they are made from carbon matter that decomposed millions of years ago. For the past several decades, biofuels have been common in Brazil, where sugarcane is commonly turned into ethanol. In the same region, there are also automobiles in Brazil that run primarily on ethanol. Another common use of biofuel is biodiesel, which is made from palm oil and used throughout Europe.


ISO 18134:2015 is broken up into three parts. Each one gives specifications to determine the moisture content of a solid biofuel sample by heating the sample in an oven. The principle behind this experiment is that once the biofuel sample is heated at a temperature of 105°C, the moisture will evaporate and the change in mass can be used to calculate the moisture content in the original sample.

ISO 18134-1:2015 – Solid biofuels - Determination of moisture content - Oven dry method - Part 1: Total moisture - Reference method should be used when high precision to determine the moisture content is necessary, and is applicable to all solid biofuels. It is advised that the mass of the test portion is no less than 300 g. However, for some fine particulate biofuels, such as sawdust, the test portion can be reduced to a lower mass.

The initial step for the procedure is to weigh the sample tray that will be used to hold the sample during heating. This, as with all other measurements in this procedure, should be marked with an accuracy of 0.1 g. The test portion of the biofuel must be spread evenly throughout this tray, not to exceed 1 sq cm of surface area per 1 g of material. In addition, ISO 18134-1:2015 advises the use of a reference tray, which should also be heated in the oven alongside the tray containing the sample. The reference tray corrects the measured weight of the tray, since the tray will weigh less when it is heated than when it is still cool. The heated reference tray determines the actual weight of the sample once it is heated so that it can be compared with the pre-heated biofuel sample.

ISO 18134-2:2017 – Solid biofuels - Determination of moisture content - Oven drymethod - Part 2: Total moisture - Simplified method is very similar to ISO 18134-1:2015, except it does not include the use of a reference tray. It is to be used when the highest precision is not necessarily needed.

ISO 18134-3:2015 – Solid biofuels - Determination of moisture content - Oven dry method - Part 3: Moisture in general analysis sample follows a somewhat different procedure than the other two standards, instead using a weighing dish and providing a somewhat different analysis of the sample. This procedure requires a minimum sample size of only 1 g. Along with finding moisture content, it determines calorific value, carbon content, and nitrogen content of the biofuel sample.

Biofuels are mainly used to power automobiles now, but they might have more applications in the future. However, many challenges exist as we try to widely implement biofuels as a source of energy. One of the greatest considerations today in regards to energy is the effect on the environment. Larger use of biofuels would require the destruction of forests to harvest biomass for the fuel. In addition, getting these materials requires a lot of energy, and burning the biomass emits carbon dioxide and other greenhouse gases into the atmosphere. Luckily, this can be easily offset by just replanting the crops that are plucked from the Earth to create the biofuel. This can also be done to offset the carbon emissions. However, this relates to the next challenge. There is only a limited amount of land on the planet, and using a great deal of it for biofuel can create competition with crops that are used for food. This could lead to severe economic defects. Ultimately, biofuels must be properly managed so that they can be used to extract the most energy from a limited amount of land without harming other industries.
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