The harm of straw entering the river? How to evaluate hazards?

Now the ban on burning straw in China is becoming more and more strict. The state forbids burning straw, and farmers have no place to pull it. Therefore, straw in many places is dragged into the river by farmers, which will rot in the river and give off an unpleasant smell. Actually, burning straw is more serious than burning straw. Burning straw is only air pollution. When straw enters the river, it pollutes the air and water. There are also many solutions. Now many people in China are aware of this straw problem, so there are many straw utilization buyers and many straw harvesting machines, such as Katie Biomass Power Plant and Hubei Yulong Machinery. One is to collect raw materials, the other is to provide random farmers with machines to collect straw in the field; The country is also increasing its efforts in this regard: some relatively rich provinces have subsidies for collecting straw in the field.