Nitrous oxide, often referred to as NOX, is a primary component in smog and acid rain. This chemical is released during the burning of organic materials, but in especially high quantities with the burning of biodiesel. This paper is discussing the use of ammonia to neutralize NOX in biodiesel vehicles; eliminating at least some of the potential pollution.
Use of ammonia in laboratory systems can almost entirely eliminate NOX pollution, but in actual practice neutralization of NOX is only 40-60%. Much of the experiment in this paper involved finding optimal percentages of ammonia, temperatures of reaction, water vapor pressure, etc. in order to optimize the neutralizing of NOX.
In addition to reduction of NOX, ammonia may also be able to reduce sulferous emissions by forming ammonium sulfites and sulfates. This would remove another harmful by-product of combustion from the atmosphere.
Diesel vehicles contain ammonia currently to help neutralize NOX emissions, but the process still requires refinement and perfection in order to keep NOX emissions low.