The corn is a nice, if generic, touch. In fact, I’d mute the header to match the tones in the corn picture, to more closely align the greens and yellows but that’s just me. Also, maybe a tag line would help add some content/excitement? For example, I have no idea what a biogas plant is – do you expect most visitors to know what it is? If not, then explain it up front and don’t keep us guessing. I like the simplicity of the design. Good luck!