Update from Bradley Watson and Garniesha Pinder in China: Turning Straw into Bio-Gas

Yesterday we visited a Bio-Gas plant that processed mostly straw into Bio-Gas. Just as straw is more difficult to process for animals than grains, it is also harder to produce Bio-Gas from than manure or sugar filled waste water from breweries. The molecules that make straw stiff also make the energy contained in the straw difficult for the bacteria in a Bio-Digester to access and convert to methane gas and carbon dioxide. This plant takes the straw and grinds it into a fine powder and then mixes this powder with warm water before feeding the mixture into a 500 cubic meter Bio-Digester. Grinding the straw makes it easier for the bacteria in the digester to break it down. The other unique thing about this plant is that they recycle the water used in the digester. The digested straw powder is separated from the water mechanically and the water is recycled through the system. This also maintains a steady population of bacteria in the system and eliminates the need for mixing of the digester contents.


This project’s startup was subsidized by the government and encourages farmers in this semi- rural community to transport their waste straw to the plant instead of burning it by offering them bio- gas at production cost. This production cost is very low because the system only requires two people to run it. On the other hand customers who do not contribute straw to the system must purchase Bio-Gas from this plant at a price slightly less than what they would pay for Natural Gas. Customers access the biogas they purchase through a distribution grid for use as cooking fuel etc.

Another note about this community is that it is near the airport and farmers used to burn their straw, which could be considered a post-harvest crop residue, instead of trucking it away. Another option they had was to truck the straw to a paper mill that would purchase it at a relatively low price. The competition between the biogas plant and the paper mill has increased the price of straw in the three years since the plant began gas production. The result is far less air pollution from burning straw and farmers can earn more money for their crops. The digested straw also serves as a good fertilizer and farmers can pick it up at a lower cost.

As countries develop and industrialize people tend to leave rural areas for urban ones in search of a better quality of life. Sadly these first generations of urbanites are often subjected to discrimination when the reach the city due them speaking a different dialect or lacking the quality or level of education a city dweller may have. They may lack the social support network they need in this new home as they search for work and raise children, and many are forced to leave their children behind. Considering this I can truly appreciate the benefits of Bio-Gas production and any other means of improving the quality of life of the rural population. Visiting rural areas has been one of the highlights of this trip for me, the air is fresh, the roads aren’t as hectic, and the people take the time to smile and try to get to know you if you make the first step.

Much Love,