Getting error while running selendroid

MacBook-Pro:~ experimental$ java -jar /Users/experimental/Downloads/selendroid-standalone-0.17.0-with-dependencies.jar
Mar 19, 2018 7:23:22 PM io.selendroid.standalone.SelendroidLauncher main
INFO: ################# Selendroid #################
Mar 19, 2018 7:23:22 PM io.selendroid.standalone.SelendroidLauncher main
INFO: ################# Configuration in use #################
Mar 19, 2018 7:23:22 PM io.selendroid.standalone.SelendroidLauncher main
INFO: io.selendroid.standalone.SelendroidConfiguration@e9e54c2[
  port=4444
  timeoutEmulatorStart=300000
  supportedApps=[]
  verbose=false
  emulatorPort=5560
  deviceScreenshot=false
  selendroidServerPort=8080
  keystore=<null>
  keystorePassword=<null>
  keystoreAlias=<null>
  emulatorOptions=<null>
  keepEmulator=false
  registrationUrl=<null>
  proxy=<null>
  serverHost=<null>
  keepAdbAlive=false
  maxSession=5
  maxInstances=5
  registerCycle=0
  noWebViewApp=false
  noClearData=false
  sessionTimeoutSeconds=1800
  forceReinstall=false
  logLevel=ERROR
  deviceLog=true
  serverStartTimeout=20000
  printHelp=false
  serverStartRetries=5
  folder=<null>
  deleteTmpFiles=true
]
Mar 19, 2018 7:23:22 PM io.selendroid.standalone.SelendroidLauncher launchServer
INFO: Starting Selendroid standalone on port 4444
Mar 19, 2018 7:23:22 PM io.selendroid.standalone.SelendroidLauncher launchServer
SEVERE: Error building server: io.selendroid.server.common.exceptions.SelendroidException: Environment variable 'ANDROID_HOME' was not found!
Exception in thread "main" java.lang.RuntimeException: io.selendroid.server.common.exceptions.SelendroidException: Environment variable 'ANDROID_HOME' was not found!
	at io.selendroid.standalone.server.model.SelendroidStandaloneDriver.initApplicationsUnderTest(SelendroidStandaloneDriver.java:175)
	at io.selendroid.standalone.server.model.SelendroidStandaloneDriver.<init>(SelendroidStandaloneDriver.java:94)
	at io.selendroid.standalone.server.SelendroidStandaloneServer.initializeSelendroidServer(SelendroidStandaloneServer.java:63)
	at io.selendroid.standalone.server.SelendroidStandaloneServer.<init>(SelendroidStandaloneServer.java:52)
	at io.selendroid.standalone.SelendroidLauncher.launchServer(SelendroidLauncher.java:65)
	at io.selendroid.standalone.SelendroidLauncher.main(SelendroidLauncher.java:117)
Caused by: io.selendroid.server.common.exceptions.SelendroidException: Environment variable 'ANDROID_HOME' was not found!
	at io.selendroid.standalone.android.AndroidSdk.androidHome(AndroidSdk.java:98)
	at io.selendroid.standalone.android.AndroidSdk.platformToolsHome(AndroidSdk.java:87)
	at io.selendroid.standalone.android.AndroidSdk.aapt(AndroidSdk.java:39)
	at io.selendroid.standalone.android.impl.DefaultAndroidApp.deleteFileFromWithinApk(DefaultAndroidApp.java:107)
	at io.selendroid.standalone.builder.SelendroidServerBuilder.deleteFileFromAppSilently(SelendroidServerBuilder.java:133)
	at io.selendroid.standalone.builder.SelendroidServerBuilder.resignApp(SelendroidServerBuilder.java:142)
	at io.selendroid.standalone.server.model.SelendroidStandaloneDriver.initApplicationsUnderTest(SelendroidStandaloneDriver.java:172)
	... 5 more