Nice Ideas!
Of course steam engines were used quite extensively in the Victorian era. They were like the traction engines used to drive country fairs and haul wagons. The had a big winch fitted underneath the boiler which pulled a sort of chariot which carried the plough and an operator and was hauled backwards and forwards across the field to plough it.
Steam engines - because of their used of low pressure steam - are only about 10% efficient. But if the fuel is cheap and readily available, that doesn't matter. Any dry waste from farming - including old bedding for animals - would do.
The gas powered lawnmower goes back to the second world war when cars were converted to run on coal gas. The gas went in in a sort of balloon fixed onto the roof of the car. Today lots of car run on compressed gas - LPG - and do so very efficiently. There are experimental cars around running on liquefied methane and hydrogen is a promising fuel for the future. All a bit high-tech for our use, I think.
Going back to the steam engine idea, I have been wondering about making one with a high pressure boiler. This would operate with a turbocharger which can now be found in almost any car scrapyard. The idea is to use it to pressurise the air entering the boiler. The escaping hot air then drives it. This may not seem much of an idea. However, it was developed commercially under the name of Velox Boiler. Have a look in Google for details. The key factor is that the boiler can then be much smaller meaning the car or other machine can have more power without getting a silly size. Fuel such as gas, oil or powdered coal can be used. just a daydream!