about the foam, you must be using one of those spinning type juicers. i would think taking the pulp and mixing that with water, shaking or put in a blender and tap it a couple of times, then strain to get more of the juice out. those things are a bit wasteful. they probably get a kickback from the vegetable growers association for every unit sold. a press is much better.
thirdly, make sure the asparagus is organic. one of the worst conaminated foods without that assurance. sorry. another reason to get every once of juice out of it.